FYI, all good DJs will pick their next song based on the crowds reaction to the last ones. The main job of the DJ is to read the crowd and know which song to play next, technical skills are almost negligible if you choose the right songs. The difference is most DJs use their own eyes instead of sending a 'crew' out to do the job for them. I don't know though, I've never seen bassnectar. Maybe he can pull such a big crowd to his gigs that he physically can't see them all and that's why he needs the crew?
I saw saw Terry Francis play 3 hours, then Claude von Stroke play a 3 and a half hour set on Saturday night. Two of the best sets I have ever seen right after each other, both such incredible DJs to play 3 hours with no mistakes!