Actually, the RIAA did instigate legal proceedings against Audiogalaxy last Autumn. That was when they suddenly made a serious attempt at blocking certain songs. Before that, almost nothing was blocked at all.
As you say, it's still p to peerless when it comes to rare material. Best of all, hardly any obscure acts are blocked. Even well known older acts like Frank Zappa have escaped blocking. This is great if your taste runs to 70s stuff and little known contemporary artists.
The RIAA has always had a strange attitude towards Audiogalaxy. Only a few weeks before the lawsuit they were favourably contrasting AG with Napster, saying that it wasn't the same sort of program at all. As AG automated music piracy virtually singlehandedly, that seemed to me a very odd thing to say. With Napster, you had to hover over every download. With AG you could go out for the evening and return to a folder full of new MP3s.
I haven't heard anything about the progress of the RIAAs litigation against AG. I love the community too and I'll be very sad indeed if they get shut down.
Personally, I believe that the ISPs are the weak link in the file-sharing chain. At present, it makes good financial sense for them to tolerate the sharing of copyright material. If the RIAA begin targetting them with expensive-to-defend lawsuits, that may change.
That will be a black day for us all.
Marius