We'll see where it goes from here, there have been similar things in the past and most ultimatly meet with failure. I see where the intent of Facebooks trademark is, or what they claim it to be. I'd imagine what happens is how many powerful people they manage to slot off in trying to enforce it. Or how bad a rep they get from being bullies, because as jerks they could go after pople using the word in chat modes, or in privatly owned fan sites. Say for example some creepy girl who is in love with the A-team's "Face Man" and makes a site involving the word face dedicated to her worship of the character and the actors who played him or whatever.
The way I see it is that if this plays out like I expect, we might see them going toe to toe with Apple, and perhaps various cosmetic companies and such selling face lifts or whatever, and having product/company based websites. As big as Facebook is, too many other big companies get involved and they're in trouble.