There's a curious attempt to sound reassuring in OiNK arrestee Alan Ellis' interview with ZeroPaid:
the logs we store aren't enough to incriminate users
This, of course, is the same Ellis who told the Telegraph that he didn't believe OiNK did anything illegal in the first place.
Now, obviously providing the means with which people can commit a crime is distinct from being involved in the crime, but it's still perhaps unwise to suggest that your users were behaving criminally.
Elsewhere, the Idolator has spoken to copyright lawyers, who shake their heads and warn that - had you been using OiNK, you should be very worried indeed:
As far as money goes, remember that "commercial advantage or private financial gain" can include the benefits of barter and the like. So the fact that, in your [description of OiNK's ratio rules], "they had to assist in infringement in order to keep infringing" might be enough.
The Idolator's brief then speculates that, should there be any action in the US, it'll take the form of RIAA moving through civil courts rather than criminal prosecutions of OiNK users; of course, the RIAA might well be happy enough with the cyber-freaking being bred in the vacuum of knowledge about what happens next to actually bother throwing money after brining real actions.
If they've learned anything from their filesharing prosecution adventures, the RIAA should know that they're more effective when people don't know what the labels might do, rather than when they show their hand and demonstrate how short their arms actually are.