Am I wrong in thinking that Facebook is only a privacy risk if you give it information you want to keep private? So if you set up an account, give it your name (or a fake name, for that matter) and then "like" something, the odds of your privacy rights being grossly violated are pretty slim.
My Facebook page has my name, my date of birth (no year) and a picture of my dog. That information is freely available to anyone who asks. (Seriously, I'll send you a pic.) The real problem as I see it isn't Facebook, it's the crazy assumption that Facebook will protect your privacy. But that's a symptom of a much deeper problem with our society that this probably isn't the best place to get into.
As for the promo itself, I don't see a problem. It's fun. Like the BioWare "guess what game we're announcing" thing from back prior to Spike, which ended on a hugely disappointing note but was fun up to that point. This stuff shouldn't be taken so seriously. It's videogames.