I would not touch any domain with "FB" "Facebook" I would not even touch social related or social service sites with "Book" in the domain.
Just take a look at any big Facebook service offering sites, every one is getting sued left right and center, so many stories about it (especially if you are located in the US). I think Facebook has a decent sized legal team just sitting around waiting for these types of sites. That guy who was offering "likes" in Brisbane was sued too I remeber Facebook has really been going after him...