Whats a DJ to do? Technically every club and nightspot is supposed to pay ascap and bmi for playing songs. Technically I'm not supposed to play any music that is copyrighted without express written consent.
While this could hurt the REAL DJ's, this could also help rap music as a whole. If RIAA goes apeshit over mixtapes it could cut down on all the half ass mixtapes people are putting out instead of doing real material.