DVD's spin 3 times faster. USB 1.1 can put out enough at best rate with a small amount to spare to burn a DVD at 1x, but that's at best rate. It will work if the data rate isn't significantly interrupted by anything else on the bus.
It will also take well over 2 hours to burn, then you'd have to wait for it to verify the burn which would take another two hours or so. Then during the verify have it say "Mismatch at Sector whatever."