I've used firewire networking back when gigabit networking was still too expensive. It does work well however a six person LAN party pushed a limit somewhere. It might of just been the crappy VIA chipset cards we were using. Otherwise I still use firewire for backing my machine up over using USB and my webcam is firewire. One of the problems with FW400 is that it's a bit of a push to stream HD from a camera and by the time FW800 was making the rounds Apple had all but abandoned it (and were rude enough to prevent devices from even charging over firewire, because apparently the thing they touted as the third coming of christ was not worth ANY level of effort) and without their push it was gradually forgotten.
I have these vibes from Apple and Intel that the same thing is going to happen with Thunderbolt. It will be the fourth coming of christ and they'll try hard to get a share of the market, then they'll drop it under mysterious reasons.

USB won because Intel was a major player there.