I once used 2 "Logitech quickcams for notebook pro" with a 10m - usb repeater and a 3m extension. It worked fine. I think the maximum cable-length for USB 2.0 is 5m. Exeeding this limit can just be done by using repeaters.
There are not many USB 2.0 Cams on the marked yet, but as I guess you are using a mac have a look for long fiewire-cables. They are working with my external Disk - so a webcam won't be a problem.
If you are using a PC make sue, that you really get a USB2 cam - with all usb 1.1 cam, compression is horrible - and your patch pretty slow.
>I would like to know if anyone has succeeded to connect a webcam
>(USB/FireWire) to a computer over a long cable extension (more than
>10 meter/30 feet).
>Which webcam model has been used?
3 firewire unibrains, daisy chained with cables of 15 & 10 meters
the first FW cable was 15 meters
it worked without a problem (except ONE crash during all the
developement/rehearsals/shows period, which is ok i think - but the
crash was on the LAST rehearsal, which makes you a little