Broadly speaking USB provides lower cost/low performance data transfer while Firewire provides higher cost/high performance data transfer. In a price sensitive consumer market vendors want the lowest cost option that provides the required feature. For data transfer, that's USB. There are MP3 players available with 5G, and larger, drives. Yes you can fill them using USB but you need to schedule it overnight. Batch jobs just aren't consumer friendly. Apple brought this point home with the new iPod. 5 gigs, 12 minutes. That dramatically improves the usability of the device. And the iPod has shown that consumers are willing to pay for it. I fully expect to see other devices with large data transfer requirements move to Firewire soon. USB will remain for devices with low data transfer requirements.

Firewire is not just for artists. Many consumer devices already use it. I'm convinced more will. If the PC makers want to connect to them, they will start including Firewire in the machines.