
It's entirely possible that the appointment has nothing to do with Perrelli's work for the recording industry. He was already a well respected Washington DC lawyer before he began working on RIAA cases and even worked in the Justice Department during the Clinton administration.
However it's also worth noting that Obama's Vice President, Joe Biden, is on the record in favor of involving the Attorney General in file sharing cases.
In any case it seems somewhat ironic that Perrelli's responsibilities will include being the top civil rights official in the US.