Facebook is suing a company called Teachbook , which operates a social networking site for teachers, apparently because it has "book" in its name and "competes" with Facebook. Teachbook is described as "a professional community for teachers". Sounds like a threat to Facebook's existence doesn't it? Do you think Facebook should be suing Teachbook? Tell us what you think . Ryan Tate at Valleywag draws on some irony , saying,