Would depend on my mood at the time, I've had a bit of a love/hate relationship with facebook, at times its been a great social tool, at others I've wanted nothing more than to see the end of it.
I've seen relationships bloom from it, but I've also seen them crumble (probably not entierly because of facebook but given the circumstances of this break up, its not hard to see some relation there). Seen old friends re-united but at the same time jerks you were glad to see the back of find you again! I dunno I could go on for hours but I wont.
Point is it would depend on my view of it at the time, disregarding the "is this a joke?" or clicking yes out of pure curiousity, because that would be very very tempting.
What would be better is a filtering process, to help remove spam bots, and remind people they dont have 300+ friends from around the world. Yes I'm cynical about that stuff. Facebook has always been for me just a way to contact close friends and family so never got the games, the adds, the people for whom they truely beleive they have all these friends and for them the website is, within reason, becoming too big a part of thier lives.
How would I do this, hell I don't know, maybe give everyone when requesting friendship a question about your life, one only close friends and family would know, if they can't answer that, no friendship invite.
Still to answer the poll, would depend on my outlook to facebook at the time (given I believed the popup), cynical day, I'd go with yes in a heartbeat, less cynical day, I'd go with no or ignore the thing.
Although as I said earlier, part of my mind would be tempted just out of pure curiosity, even more if it then gives me a window of hidden cameras in everyones houses as the realisation dawns. Now theres good reality TV!