Random question of the day

What's the Facebook protocol for dealing with someone with whom you were only Facebook friends because they were dating one of your friends, after they break up with your friend? Assume that it wasn't a particularly horrendous breakup (in which case an ostentatious de-friending might be in order), but you're certain you'll never see them again, and don't want them cluttering up an already cluttered Facebook page.

Yes, I am feeling about 12 today. Work with me.