New Facebook app, once your friends change their relationship statuses, the app will email you. which Gawker said for the lazy stalker. Is theres any lazy stalker? But, maybe the main point for this is, from the site:
You like someone. They’re in a relationship. Be the first to know when they’re out of it.
Its for the stalker, who wants to be the first to notice the availability for his/her friends.