Sorry, this is rather unwieldy and probably merely exposes my fundamental ignorance of all things economic...
I hate corporations. I really can't think of any company I would unreservedly support on all aspects of their product line and business model. Google comes closest, I suppose, but I can't even think of a first runner up...and while I like Google, they're certainly not perfect either. Obviously corporations are necessary since we can't all grow our own food and make our own cars and TVs and clothes and such these days since all of our very specialized knowledge and skills leave us unable to do much of anything else and because there's almost certainly someone out there better at inventing/making an X than we are. In theory, I will admit capitalism sounds like a good idea. Division of labor, competition, efficiency of markets—all this sounds great. Unfortunately, the real world doesn't seem to reflect the theory at all.
The general thought, or so I am told, is that in an open market, consumers purchase what best fits their needs, so the company that provides the best products makes the most money, and everyone (well, that company and the consumer pool as a whole) wins. Eventually one would assume other companies get the idea and make similar/better things, introducing competition (including price competition) and making the consumer even more likely to get exactly what he or she desires. I'm sure this is actually the way it worked in the very beginnings of capitalism, but it certainly doesn't anymore.
First of all, no matter how a market should behave, it never quite does because it's full of people who don't exactly act rationally in their own self-interest (shocker). People buy one brand over another because they like the packaging better, because they like the ads better, because it's the brand their parents used or that they have always used (particularly with personal care products like shaving cream and feminine hygiene items, lifetime brand loyalty is ridiculously high and surprisingly affected by parental use), because it's the only brand that works with their other related device (iTunes; video games and gaming systems; printer cartridges; razor blades), because it is carried in more stores, because it has an image that they like, because it's the only thing available (utilities companies that are the only companies available in certain areas), etc. A brand of soap could easily be better than the one someone has used for ten years, but people don't regularly have blind soap-testings to see if maybe their wallets should be voting for a better soap. Maybe Rock Band is superior to Guitar Hero, but if everyone has Wiis, everyone's going to be playing Guitar Hero instead. How is this the exercise of freedom of choice and rational weighing of the options? (Even if someone does regularly switch toilet paper brands to see which is the best, if everyone else is just using one brand because that's what they grew up using, it will be to no avail. Heaven help the poor lone rational actor.) I thought economists had recently 'discovered' this irrational phenomenon (judging by the recent spate of books, at least), but that hasn't seemed to significantly undermine faith in markets.
Even if you were entirely rational and made the best decisions for yourself in alignment with your principles, how exactly does one go about voting with one's wallet? If there is an infinite array of every possible choice, then it's obvious that simply selecting and purchasing the one that best fits one's needs will work quite nicely, registering one's preferences and encouraging companies to do more of what that company/product did and less of whatever is entirely undesirable.
In real life, though, there aren't infinite choices. If you want a computer, your infinite options are suddenly very limited in scope. You get two options (assuming average computer literacy): Windows or a Mac. Find Microsoft and Apple equally repugnant? Too bad. Want something more intuitive than Windows but less expensive/interconnecting/trying-to-run-your-entire-life than Apple? Again, good luck. In many situations, perhaps even most, the option you actually prefer isn't even available.
Now, I assume the pro-capitalism response to this would be that if nobody makes what you want, you can always start a company yourself to fill the gap. Obviously a nice sentiment, but come on; you obviously can't create a phone, a car, a TV, all the clothes you ever need, a health insurance system, and a food supply system that will best serve you all in one lifetime. There's way too much expertise you don't have and don't have time to learn. Plus, isn't that whole point of having companies exist—the division of labor? I would guess the more reasonable pro-corporation response would be that if there's really an unmet need, a gap in the market, someone will rise to fill it. Yes, well, unless it's less likely to make them money for some reason, or if the demand isn't high enough, or, or, or...any one of a number of reasons.
Doesn't constant competition in a market actually make it less likely that the best product will ever be created? Even if everyone is vaguely dissatisfied with the current offerings, they will likely still select what they consider to be the best available option, and there will likely not be a raucous demand for a better widget since this one is good enough. Never mind that much better widgets could easily be made; it's not worth someone's while to make them and then worry about how they're going to brand them, advertise, and get enough market share to make it worth their while.
Speaking of advertising and marketing, they warp the competition even further. It quickly becomes less about which brand of thingummy-bob is actually better and more about who has the best ad ideas or the most effectively designed marketing campaign. (Obviously advertising doesn't move people who are passionate fans of Brand X to consume Brand Y instead because it has funnier ads, but for people who have no strong feelings or who aren't fully informed, brand preferences can be easily influenced by the quality or ubiquity of advertising.) Brand recognition is also a problem for anyone trying to improve the market in any area where there are already entrenched competitors. Nobody wants to switch to the unknown because nobody else is using the unknown. Better to keep using an iPod because everyone else has one than to take a chance on some no-name MP3 player, right?
Then there's the problem that consumers often don't even have access to the information they would require to make rational decisions. Say someone only wanted to buy meat that had been raised humanely. Until very recently, they would be entirely unable to do this as nothing was labeled as cage free or free range or organic until enough people made enough noise. Say someone wanted to select which cell phone to buy based not on price or available service providers or features but on some other less popular criterion. Good luck trying to figure out which cell phone currently on the market has the smallest carbon footprint or is made by workers who are exploited the least.
...Which leads to my primary concern with the market system. Given that one's wallet can vote based on various aspects of the product in question itself (price, color, size, function, features, durability) or on any given aspect of the company as a whole (business ethic, country of origin, environmental effect, labor practices, humaneness, ingenuity, charisma of the guy in charge, or simply the fact that it's the best-known and therefore is assumed to be the best, period), how is the market supposed to effectively transmit all these choices to the companies' decision-makers? What happens when a company thinks people are buying all their stuff because their ads are awesome but people are really buying their stuff because of their decent labor practices? They'll spend more money on awesome ads, which would be kind of unnecessary. Or what if a company interpreted their high sales as consumers saying their features were better than their competitors' features but in actuality, their competitors have shoddy environmental practices and nobody wants to buy their stuff to send them a message? They won't try to improve their product's features because they think people love them, even if they're not even as good as those of the competitor.
Obviously it would never be the case that consumers as a whole would have the same response to any given aspect and that the company would entirely misjudge a giant movement, but I think that even makes my point stronger. With so many competing groups making purchasing decisions based on so many completely different aspects, how is anyone supposed to figure out what's actually working and what the consumer wants? I guess the idea is that it doesn't really matter, and if slightly more people favor one thing, it will have an advantage over others, regardless of whether it was preferred because it came in cute colors or came from an environmentally conscious company, and then the company and its attitude toward design and production and labor and environmental practices, etc., will hold more sway in some greater uber-market. Nice thought, but most of us want our better computers, toothpaste, or jeans now, not when the market finally subtly shifts in three decades to reflect the choices consumers are making now.
To me it really seems like consumers, rather than simply voting in a clear-cut manner on whether Product A or Product B is the best, are involved in complex behavioral shaping attempts. Oh, good, you quit exploiting Asian workers for pennies a day! I guess that means I can buy your products now since everyone else is still doing that. Oh, look, a slight design change. Yeah, I don't care so much about that; no reward for you. Urg, your CEO is kind of a jerk; maybe I'll show my disapproval of his comments by boycotting your products. Hey, your new source for raw materials is deforesting the earth at an even more-rapid pace than the last one—I'll stop buying your stuff even harder! (Great, I'm sure that last message came through loud and clear, considering there's no way for them to even note that change in your opinions.) Shaping works all right to train pigeons to perform tasks like pecking buttons to get food, but I'm not all that convinced it would work very well to convince unwieldy corporations to behave in accordance with your system of ethics all while producing stuff you actually like and that will improve your life.
(Obviously corporations don't actually care what you think, and I don't guess the free market really cares if you feel fulfilled and happy either, but still, doesn't it seem inefficient to anyone else to have no clearer way to communicate than through a simple up-or-down buy-or-not vote?)