I don't think you understand how DDoS works on this level. Your UDP stream would have to have a source, which would have to have an IP, which then would get flooded to crap. It's the routers that pop, not the machines.
The point is that
when merely using UDP, unlike TCP, the source can block ALL incoming traffic which makes it immune to DDoS. As casascius points out, UDP is like a radio broadcast signal. TCP is like the postal service with delivery confirmation.