Hipsters to me are people who, like others have said, take bits and pieces from other cultures but only because they're cool, not because they like them. They're the sort of people who would look down on you for wearing some sort of clothes, but then wear them two years later because now they're cool. People who like certain things only because they're "cool".
I don't necessarily have a problem with a "cosmopolitan" attitude towards life, taking bits and pieces from other cultures, as long as you don't pretend to belong to those cultures and that you would die protecting them. You know, if you say, "I think that *this principle* from *random philosopher* is interesting, but I don't really agree with his other ideas, and I think *this idea* from *this book* is interesting, but I don't really agree with the other ideas" that's fine by me. But don't call yourself a supporter of Ghandi or something just because you read an article about him online and thought he was cool. I don't call myself a "traveler" or a "wanderer" because I've never traveled. Or wandered.
I guess we can all be guilty of this at one point or another when we're overenthusiastic, but I think with most people, that falsity goes away once they become more educated about what they like. I guess it's the fact that "hipsters" just keep liking things that they don't even like just because it's still cool and to say they don't like it would lead them to being judged by their friends.
For example, there's been this big thing with high-school age kids that shopping at thrift stores is cool. And it really fucking annoys me that all the people that would scoff at people who wore anything that wasn't from some big brand are now all singing "Thrift Shop" and bragging about how they got their clothes at Goodwill. Now everyone's saying, "oh, it's not cool to brag about your clothes, blah, blah, blah" (when six months ago they were doing just that) and don't realize that they're doing the same thing (again). Just because you're bragging that your clothes come from a thrift doesn't make bragging about what store you got your clothes from any less stupid. If you only want to wear thrift shop clothes, fine by me. But you should be wearing them because you want to, not so you can talk about it later.