I know -- I've seen that. It's possible that late-stage Open Firmware changes were made to support that configuration, but I cannot reproduce it on a number of USB2 PPC Powerbooks I have here. And my communications with Apple -- and knowledge base articles at Apple -- indicate that it won't work.
But, even if true in some limited circumstances, USB2 drives are
much worse than FireWire drives. They're slower, deal less well with other devices on the bus, don't provide as much current on the port... avoid if possible!
