"No....thats not true, thats impossible!!!!"

- Luke Skywalker, Empire Strikes Back
Firewire and USB are two very different technologies, better suited for different things.
Firewire is a peer-to-peer bus, and being so, you can use it for networking and Firewire Disk Mode. Most DV cameras nowadays have Firewire ports, and a lot of Mac users make movies with iMovie. Firewire has six-pins: four for data, two for power
Firewire hard drives have not only faster transfers, but in my experience have more reliable transfers.
USB is a master/slave bus, and is therefore best suited for general peripherals like mice, hard drives, printers, and iPods. It has
Also, speed-wise, Firewire 400 decimates USB 2.0.
http://www.barefeats.com/usb2.html