Posted by Jason in 
Muxtape seems to have been voluntarily taken offline due to some issues with the RIAA. The site is inaccessible and has this message:
Muxtape will be unavailable for a brief period while we sort out a problem with the RIAA.
And from the blog:
No artists or labels have complained. The site is not closed indefinitely. Stay tuned.
Beta users of Muxtape For Bands: you are unaffected by this outage.
The issue is understandable seeing as how fast the popular mixtape site gained traction, other music streaming and playlist sites are required to pay licensing fees. It was only a matter of time before the RIAA took notice.