Of course, these cams natively support Win32 OSes, and Mac support is spotty.
And Apple's iChat natively unsupports USB cams. (iMovie is the same, it seems)
So, to get a 50 dollar camera to work on Mac OS X Tiger, you need a third-party driver (trialware, $24.95), and to get it to work in iChat you need, well basically another thirdparty driver kludge (trialware, $9.95) .. == $35 of additional software.
Of course there is a stable, free Linux driver and lots of software of all sorts, in various stage of completion. Oh, and there's a script for Ubuntu that does the setup for you for any supported cam.. which seems to include the previous two generations of usb cams at least. Apps like Kopete and GnomeMeeting are alleged to Just Work (tm).
And oh look, it's bedtime. I am sooo looking forward to being able to Xen away MacOS when it pisses me off.