Facebook (500 million+ users) is suing the people behind Teachbook (fewer than 20 users) over their use of "book" in their name. This is another sad example of the 500 lb. gorilla knocking the little guy around. No one is going to confuse the two or start thinking that "book" is somehow getting diluted. Which one do you think has the money for a court battle like this? Right. So, who wins nearly by default. Right. Sad but true.