This gets very meta very quickly. If linking to copyrighted data 'should' be illegal (SOPA), then what about descriptions of that data that are sufficient to identify the original, but not reconstruct it (magnet links)? And if those were made illegal, then what about descriptions of those descriptions? You can recurse infinitely on this. Beyond mere amusement, after just one or two recursions, you get to the point wh…
A description of copyrighted data would be the torrent file, which content producers would probably like to argue are infringing.
A magnet link is a hash of the torrent file, so it's already two steps removed.
Of course, the Pirate Bay magnet dump is itself a torrent, so it's a hash of a hash of a hash of copyrighted data.
And that torrent itself has a magnet link: 938802790a385c49307f34cca4c30f80b03df59c is a hash of a hash of a hash of a hash of copyrighted data. (In the MP/RIAA's ideal world, I've just committed criminal copyright infringement with damages reaching into the $billions.)
Theoretically, the Pirate Bay dump could include the torrent for the Pirate Bay dump, and be an infinitely recursive description of itself... but that's probably an intractable cryptographic process.