A MONTH BEFORE Atlanta hosted the first hip-hop-focused spinoff of the BET Awards in 2006, an executive at the cable network joked the event would likely not benefit the local economy. He was probably right. Rap dollars already coursed through the Southern city like its ceaseless traffic, bankrolling recording studios, propping up nightclubs and music-publishing companies, and sustaining a vast corps of DJs, strippers, bodyguards, and lawyers. After the inaugural BET Hip Hop Awards aired and nearly half the honors went to Atlantans, local rapper T. I.—who won four awards that night, the largest