One element left out of Brett Gaylor's Rip: a Remix Manifesto is that of the remixer/reuser's attitude toward the past. The implication is that it's benign, merely using what he/she finds to make new art. But it's rarely that simple. Led Zep didn't merely borrow from Willie Dixon and Robert Johnson; they made made them "now" because now is better than then. There's an implied condesention toward the past, one often epressed by remaking it in a contemporary image.
In Girl Talk, the past is updated by being laid over new beats, taken out of context, and often given a new vocalist. That'snot a neutral act, even if it's done affectionately. As he screws with classic rock, you know he's upsetting many bands and their rap-hating fans by laying emcees over their riffs. But Girl Talk's am equal opportunity irritant; I'm sure many hip-hop fans are just as horeified by some the lame aongs their favorites are paired with.
But if the past tries to control the future and fights the present, it's not simply out of greed or small-mindedness. It is under attack by the forces of now, just as it always has been.