I don't really know that many people that are sheep, mostly because I hang out with the social rejects, the "rebels", and the people who don't really give a crap and like the group for its individual members, ie me.
But I do know what you mean, to a certain extent. I don't think I've ever sold out my ideals to like something others like and become popular, but I have done the opposite on many an occasion. For example just last night, I was at a videogame party thing, and they decide to pull out Call of Duty 3 or 4 or whatever. Being anti-first-person-shooter, I instant get annoyed and wait for half an hour as they play the first round. Second round, I say screw it, join in, and to my own disgust, I find I actually enjoy it. I won't be going out to the stores to pick a copy up, but if we ever get together and play it, I'll join in.
Anyways, I'll leave off here, because anything else I write will ramble off into a completely unrelated direction.