VanityGirl said:
http://www.somethingpositive.net/sp08312004.shtml . It fits.
More on-topic, though: I think it has to do with the fact that most of us spend so much time outside of the mainstream that we've come to associate the mainstream with "what sucks". At best, it's because we're independently minded, and not willing to just fit in. More likely, it's because none of us were really "cool" in our young lives, and as a result backlashed against it. In order to make being an outcast survivable, we have to denigrate those things which are in the mainstream, and make ourselves "rejected because we're too good".
It's all about loci of control, yanno? We want to believe that we're choosing to be separate from the prototypical "popular" things, because if we're choosing it then it's something of our own volition (and thus not a rejection). If we're just being told we don't deserve to be popular, it's a bad feeling. The illusion that we could be popular/mainstream, and choose not to, is more comforting than the probable reality that we've always been forced to the periphery.
(ZHU) Michael said:
Ehh. It's possible, but that ignores that we deride things in the mainstream because they're mainstream. We love bands like Neural Milk Hotel primarily (I believe) because they're "independent", rather than because the music is actually better. If you're not liking a specific movie/show/album because it sucks, that's one thing. What we're talking about is deriding things simply because they're popular, that's different.
Popular things can suck (Transformers). Indie things can suck (I hate, for instance, Animal Collective). We embrace indie, I believe, because of our individual histories of being rejected by the "popular" elements and reconstructing our own internal narratives to read less like "I was told I'm too ugly/annoying/poor to be one of the "cool" kids" and more like "I don't want to be one of the cool kids, 'cause I want to be independent and do things my own way"