"For the past several months, we have communicated our legal concerns with the site and repeatedly tried to work with them to have illegal content taken down. Muxtape was hosting copies of copyrighted sound recordings without authorization from the copyright owners. Making these recordings available for streaming playback also requires authorization from the copyright owners. Muxtape has not obtained authorization from our member companies to host or stream copies of their sound recordings."
Interestingly the RIAA didn't say that Muxtape had failed to respond to RIAA (presumably DMCA) requests, but the double up on the copyright side makes Mixtape's attempts for survival that much harder; not only are they being pinged for hosting (the obvious first call as we noted yesterday) the RIAA is targeting the unlicensed streaming aspect of the service as well.
Muxtape would seem to be completely screwed here. They have no clear revenue stream, and even if they did they probably couldn't afford the fees the RIAA will be demanding to keep the service online. Muxtape is officially on dodo watch.
See also Cyndy Aleo-Carreira excellent piece on the music industry here.