Perfect 10 is a company that, for a brief period of time, apparently published a rather expensive porn magazine. Since then, it seems to have served a single purpose: to file ridiculous copyright lawsuits that it almost always loses, but which have helped to define case law concerning copyright issues.
Perfect 10 Loses Again, As Court Says DMCA Notices Need To Be Properly Filed
In Perfect 10 v. Google, Round 3 Goes to Google: No Sloppy DMCA Notices
EFF Comes Out, Guns Blazing, In Countersuit Against Righthaven & Stepens Media
The Las Vegas Sun has a good overview of the counterclaims and defenses. Helping out the EFF is Andrew Bridges, who is known for challenging questionable copyright lawsuits with creative, but solid, defenses — so some of the defenses here shouldn’t be all that surprising.