Some USB video devices simply will present an on-screen dialog: "This Device Requires A USB 2.0 Port".
Frankly, Macs lacking USB 2.0 ports have hit obsolescence anyways.
And unfortunately, Apple doesn't have a Webcam Preference Pane in OSX.
It also provides alot of webcam effects to play with.
Several companies such as Rocket Fish, HP, and Microsoft have 1 or more buttons on the camera to save an image snap to disk, send to email, or possibily to a printer.