EFF's Fred von Lohmann addressed sites like Muxtape in a News.com article, saying that in theory they should be protected by the Digital Millenium Copyright Act. But the devil is in how small companies comply:
Whether the safe harbors will cover their businesses is difficult to predict in the abstract, since much depends on whether they have complied with all the prerequisites in the statute," von Lohmann said. "But there is no reason, in principle, that they should be any more legally vulnerable than Google/YouTube. Of course, that's no guarantee that they won't be sued.