I'll start by saying that because of the technology rush in the last decade, sadly anyone or everyone can consider themselves to be a dj. Get yourself a decent computer, buy the most fitting program that caters to your needs, up and download a rush of the hottest mp3 files, and boom.... you're instantly whoever your favorite dj is (in your mind and dreams that is).
Before the computer, the dj was the backbone of many hip hop groups that kept the party grooving before, during a stage show, and way into the morning light hours. And to have that honored position, you had to be GOOD, meaning having your own sense of style while keeping the spot bumpin'. Dj's entertained and TAUGHT the crowd about music that they might not have known about and MADE them like it by the way they rocked it into the mix. NO ONE told them how or what or when to play. Many times the turntables were either elevated above the crowd or closed off. If you even tried to step beyond the barrier, you got shut down QUICK by security or the dj's boys who craved to handle the trespasser. I've seen it happen.
I have a few points.