First, the bad news: If the government wants to go after you, Demonoid user, they've got everything they need. According to a source at Demonoid's Ukranian data center, “Investigators have copied all the information from the servers [for] Demonoid and sealed them.” Because Demonoid served as a torrent tracker (both hosting torrent files and coordinating file transfers between peers), those servers contain more than enough fodder for a lawsuit.
The good news is, it probably won't happen. "As a practical matter, the US government has not been aggressively prosecuting individual file-sharers except when there has been an impossible-to-ignore infringement of high-profile assets, such as the pre-release of a Hollywood blockbuster movie," Eric Goldman, Professor of Law at Santa Clara University, told me. That's why all the recent takedowns, from OiNK.cd to MegaUpload, have gone after the site's owners instead of its millions of users.
When individual users are named, it's usually on behalf of individual works, like The Expendables or The Hurt Locker, rather than the sweeping RIAA lawsuits we saw pre-2008. (Even those had their problems.) A suit like that might use Demonoid's data as fodder, but it wouldn't give them much of an edge. It would be easier and more comprehensive just to follow every torrent of the movie, regardless of which tracker it's using.
All of which is to say, you're probably safe. At least on the Demonoid front. But maybe stop stealing things anyway?