I don't really understand this whole thing. Why did they decide that performers suddenly have the right to additional compensation and who gave them the right to decide? You would think that online services would just have to pay a blanket fee to ASCAP, BMI and SESAC, just like the broadcasters and that would be the end of it.
ASCAP, BMI and SESAC do not benefit the performance, just the writers and composers.The only case where a performer gets any payment from one of the three is if they also wrote the song they sing.
The underlying reason for the DCMA is that digital copies of audio or video can be re-copied over and over with no degradation, and easily distributed. A digital copy is essentially like handing consumers a master disk back in the 70's. So there was a rethinking of the whole performance copyright thing based on the new reality. (Caveat: extreme simplification)