I agree that homogeneous Abercrombie frat guys are douchebags. At my school we called them Heh Heh Hehs. They were actually smart, but anti-intellectual, and usually headed for a career in private equity or something like that.
So I think the GenY definition of douchebag as an muscular, tan, Ed Hardy-wearing guy with slicked hair is funny, but too narrow. A douchebag is a narcissistic guy who thinks he’s cool, and surrounds himself with guys who dress, look and think just like him. He’s superficially attractive but lacks depth. He’s oblivious to his douchy appearance and behavior. He’s probably talking loudly on his cell phone in an inappropriate place right now.