I think the word "hipster" is thrown around way too much these days. I don't think anyone who's into the arts and might dress "indie" is automatically a hipster.
To me, it's all about the attitude, and the wardrobe/trends that everyone focuses on follow that. It's a value on details that most people think aren't significant, and a sense of superiority because they have that value in those things (environmental issues, obscure art, independent music, etc.). They need to be seen with this value, so others in that same group accept them and they have a place to belong. But because most people don't share or understand this value, they are labelled as hipsters. The problem often comes when the hipsters themselves don't understand why they have that value and are just doing it for the trendy factor that comes with it.
To be honest, I dislike most of the people who hate hipsters more than the people being labelled as hipsters. Does this make me one?
On a kinda related note, skiers share so many qualities with hipsters. Huge value in style/clothing/gear, but focused on what others think of our stuff instead of doing it for personal reasons/expression. Wearing things that make the majority of people think we look retarded, but we think we look "steezier" than they are and are better as a result. Basically the exact hipster mentality, and I admit I used to share it.