[ggchappell]

I think some of us need a bit of a primer on trademarks.

A trademark does not restrict arbitrary use of a term, but only uses that conflict with available product. Off the top of my head, consider Nestle's (former) trademark for "tollhouse". This referred to the cookie. You could not legally sell your own cookies and call them "tollhouse cookies". But you could still sell, say, a booth for collecting highway tolls, and call it a "tollhouse".

So, no Facebook is not claiming complete ownership of the word "book" -- or, if they are, then they're wrong. They are claiming that you can't use it to conflict with their usage of it. So sell some software for recording purchases, and call it "checkbook", and you're fine. But make a social website called "friendbook" without their permission, and you'll get sued. You'll lose, too; and that is not a bad thing.

P.S. The law already restricts usage of trademarks. Adding this to their license, as far as I know, changes nothing.

Disclaimer: IANAL. Input from actual lawyers would be good.