Sounds like something that I have seen/heard at a couple of dev shops. Break the build, buy doughnuts for your team. Not too expensive so as to ruin the person, but enough of a token that you think about what you're doing.
(Aside: how many articles was Joel planning on writing when he came up with that URL scheme? Crikey.)
Some teams want everyone to be familiar with how they do it. If that is your goal, you have to pick the unlucky person in some way.