This isn't even the first time this has happened. Remember when they renamed Libra? I think they just assume it doesn't matter, and if it does, the settlement will be a blip. It doesn't always work out that way for them.
Trademark-wise, "Facebook" and "Book of Faces" are different things.
It's trademark.
Yeah, they keep forgetting they still have to follow the law, because society hasn't yet collapsed into a cyberpunk dystopia where big corporations are totally above it.