I contacted these guys about this specific situation .. because I have a Canon ZR-10 that I'd like to hook up to my iBook. Anyhoo, go here and give it a try. They tell me it should work perfectly with OSX, let us know if it does though.
(I would try it out but I just haven't had the time)
Honestly, I don't know. I'm assuming that just like everything else .. the companies are slow on updating their drivers. Webcam's aren't exactly a NEED NOW product like printers, so the cam companies aren't in any big rush to push out support for a new OS. Especially when they don't gain any immediate financial benefits.
I know Logitech and iRez are working on drivers for their USB webcams. FireWire cameras all work fine with X. Just keep emailing your tech-support peeps and nag them to death until the new drivers come out.