There never would have been a bust if they didn't think they would have anything.
Just wait until they finish going through the seized stuff - if the admin kept records or as IP info with user/pass or any other kind of info, there's just no telling what will happen ya know. Just because the guy is out doesn't mean anything really.
Well, heres the thing. OiNK encrypts the IP's, so all the feds have is the hashes of the IP's, and theres no legal way they can obtain the true IP from there. Another thing, theres 180,000 members on OiNK, it'd be too mcuh time/money/effort to spend when all they have is an IP address, which the alst time I checked is no longer enough to convict, and when its just a hash, that's next to nothing. They let him out, because they couldnt charge him, since music itself wasn't on the website, it was just a bridge to a torrent, and it can be argued that the website itself did not do anything illegal.
Also, it was English police that did the raid, as of right now theres no US involvement, the web server was hosted in Amsterdam, so all things considered, I really don't think theres really any need to worry.
Heres an interview with the OiNK founder himself, and I think he's putting himself in a very good position to win this case.
http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2007/10/25/ninternet125.xml
Also, Demonoid, another popular private torrent community has been raided twice, and not only won over authorities, but they are still running this very second.