Facebook has milked the vanity URL deal for all its worth until this point so why not try to get a little more mileage out it, right? Over the past few months Facebook has been allowing individuals to choose their username but has put the rather strict caveat on the practice that it is a “one and done” proposition. In other words, when you make that fateful decision to make your vanity URL something that was something funny but not very practical you were stuck with it. Well, the mighty Facebook is showing its merciful side by allowing users to pick another username. Beware though, you only get one shot …… again.