Facebook is known for going after any company that uses the word "book" in its name, having already filed suit against TeachBook.com, FacebookOfSex.com, and most recently UK adult dating website Shagbook.com. The last one is fighting back; Shagbook has filed its own opposition, along with counterclaims, with the United States Patent and Trademark Office.
Shagbook allows consenting users to carry out location-based searches in order "to hook up with local singles for no strings attached adult dating" in Australia, Canada, Ireland, New Zealand, South Africa, the UK, and the US. In May 2011, Facebook filed suit against Shagbook, saying it would be "damaged by the issuance of a registration for the mark Shagbook."
As represented by SNRG Ventures, Shagbook has in turn accused Facebook of trademark bullying and says it has been "abusively using oppositions, litigation, and threats of the same to maintain a competitive market advantage," according to a US Patent Office Filing (PDF, via Paid Content). In the filing, Shagbook also "denies the allegation that Facebook is highly distinctive as it is a generic term."
The filing goes into the history of the term "facebook" and argues that it has been used for decades to describe publications created by students, faculty, or staff at colleges, universities, and even fraternities. Typical facebooks contain at least pictures and limited biographical data. Shagbook not only argues that facebook is a generic term, but it challenges the validity of Facebook's trademark, arguing that it should never have been granted.
It's worth noting that if you search for "facebook" on Wikipedia, you are automatically redirected to wikipedia.org/wiki/Facebook. At the top of the page, there's a short message: "This article is about the website. For the collection of photographs of people after which it is named, see Facebook (directory)." If you click on that link, you'll be redirected to wikipedia.org/wiki/Facebook_(directory), which describes the term as so:
A facebook is a printed or online directory found at American universities consisting of individuals' photographs and names. In particular, it denotes publications of this type distributed by university administrations at the start of the academic year with the intention of helping students get to know each other.
Facebook insists Shagbook is in violation of Facebook's trademark because the site's name is highly similar in "appearance, sound meaning, and commercial impression" and that the name was adopted with "the intent to call to mind and create a likelihood of confusion … and/or trade off the fame of Facebook."
Shagbook's founder, whose name is unknown, points out that his website was created in 2006, long before Facebook became popular. He is an American has spent many years living in the UK and has been using the term "shagbook" prior to the launch of Facebook or Shagbook. Last but not least, Shagbook is specifically for dating, while Facebook is a general-purpose social networking site, so Shagbook argues it's unlikely that consumers will be confused.
In short, Shagbook hopes Facebook's history of tough trademark enforcement could result in Facebook's trademark being revoked.
Facebook's original filing against Shagbook, and Shagbook's counter filing are included in full below: