If you're thinking: oh, this is a cool move from the RIAA, finally not afraid to show the general public what they're really stand for, you're wrong. The RIAA opposed the broadcast; it was requested by the defendant's attorney, Charles Nesson.
Judge Nancy Gertner approved this request for fairly obvious reasons; the RIAA clearly said, many times, that they're not going after one file sharer; they want to warn the wider public that file sharing is wrong. Therefore, she said, "their strategy effectively relies on the publicity resulting from this litigation." Or, in other words, the RIAA must choose: do they really want the publicity or not?
Personally, I love the idea. Of course, most people probably won't bother to endure listening to the entire thing, but those who are really interested in the subject matter (and who understand the language of law) will finally be able to see what's really said at these hearings, especially since it's very rare for courts to allow live video feeds from the courtroom.