I've been forced to watch The Hills exactly once. I think the show's success signals the decline of North American culture* but we are culturally compensated for it when the "stars" of the show appear on The Late Show. These appearances are a deep, plentiful vein of uncomfortable humour which, at its best, surpasses the greatest episodes of Curb Your Enthusiasm or the U.K. version of The Office. Letterman refuses to simply give reality TV stars the privilege to be considered celebrities; he toys with them and forces them to justify their presence on his couch. In his interviews with Lauren Conrad, Dave balances a clear infatuation with Conrad with a bemused sense of wonder that these people are being paid money for what they do.
Even better is Dave's interview with Spencer Pratt, where he makes no attempt to hide his utter contempt for Pratt as a human being.
Dave: What do you do, exactly?
The lack of any self-awareness on the part of the show's cast members takes the comedy to a level of high absurdity. I hope The Hills lasts for another 5 seasons just so Dave can continue to interview members of the cast.
*replace this with any other statement calling popular culture stupid here.