I don't feel 100% qualified to dive in too deeply with my own words, but this article dives right in:
http://nymag.com/news/features/69129/The crux seems to be:
> [The] hipster—and the reference here is to Norman Mailer’s “The White Negro” essay for Dissent in 1957—was explicitly defined by the desire of a white avant-garde to disaffiliate itself from whiteness, with its stain of Eisenhower, the bomb, and the corporation, and achieve the “cool” knowledge and exoticized energy, lust, and violence of black Americans...
> The hipster, in both black and white incarnations, in his essence had been about superior knowledge—what Broyard called “a priorism.” He insisted that hipsterism was developed from a sense that minorities in America were subject to decisions made about their lives by conspiracies of power they could never possibly know. The hip reaction was to insist, purely symbolically, on forms of knowledge that they possessed before anyone else, indeed before the creation of positive knowledge—a priori. Broyard focused on the password language of hip slang.
> The return of the term after 1999 reframed the knowledge question. Hipster, in its revival, referred to an air of knowing about exclusive things before anyone else...
The rest of the article is sort-of a history of various trends in "hipsterism" over the period from 1999 to 2009. But this is quite a digression from the dominance of jeans...