MediaPost reports that Facebook has filed a complaint against Teachbook in U.S. District Court for Northern District of California for trademark infringement. This appears to be your classic trademark infringement dispute. Trademarks are used to identify goods in commerce. Facebook claims that Teachbook's name will confuse people into thinking its products are Facebook's. Teachbook volleys back and says that no such confusion exists.
Teachbook, according to its website is "a professional community for teachers" who can join and then, "create, share and search a database of lesson plans and instructional videos...."
The case is Facebook, Inc. v. Teachbook.com, No. 10-3654 and Judge Ronald Whyte is presiding.