An adult-oriented social networking site has fired back at Facebook in court, denying that it is infringing on any of Facebook's trademarks and filing a countersuit.

Facebook filed a lawsuit in April against four companies: FriendFinder Networks, Various, GMCI Internet Operations Inc., and Traffic Cat. The first operates a site called FacebookOfSex.com. Facebook says the adult site infringes on its trademarks, and associates Facebook with pornography.

FaceBookOfSex includes features that allow people to find friends, as well as upload photos. It also includes the ability to keep up with other users' activities, in a way that Facebook says is too similar to the news feed feature it offers.

Facebook is also suing several John Doe defendants, which it says Friend Finder Networks encouraged to infringe on the Facebook trademarks as well.

Friend Finder Networks says, in its answer to the complaint, that the other companies in the suit are not subsidiaries of Friend Finder. It also says that the term face book is generic enough that the company has a right to use it. More to the point, it isn't likely to confuse consumers. On top of that, the use of terms similar to Facebook could be construed as parodies, which are protected.

The countersuit says that the term friend finder - as used by Friend Finder Networks - predates Facebook by several years. That, the suit says, puts Facebook in the position of infringing the trademark, as Friend Finder is used as a brand name on Facebook's site.

Included in the complaint is a string of emails between the companies. They show the two companies discussing when they might meet to work out their disputes over intellectual property. In them, Susan Kawaguchi, Facebook's domain name manager, says Facebook is concerned about several domain names including Facebookofsex.com, Penthousebook.com, and Myfaceonpenthouse.com. (Friend Finder also publishes Penthouse).

Meanwhile, David Bloom, Friend Finder's general counsel, also says he is concerned about the use of Friend Finder on Facebook's site. He also says he wants to discuss your suggestion that our use of Penthouse when combined with either the term book or face infringes upon Facebook's IP rights.

The case is being heard in the U.S. District Court for the Northern District of California.