Don't think so. It would be really cool though. Booting from a thumb drive in time of need would be very helpfull to me when I am in the Windows world.
Shouldn't any of the 1 or 2GB USB flashdrives be able to hold OSX. (I have a 2GB that cost me an arm and a leg, but I use it for work so I'm not about to dump it to try this OSX experiment)