Well, back in the day (~'95 or '96) there was a connectix quick cam made for a mac that I think used a serial connection.
Actually, most likely (though I never saw it, so I don't know for sure) it used the ADB connection on the Mac; while such a connection theoretically allowed for a higher-speed data rate than a regular serial port - supposedly it wasn't really possible, unless they were doing some software trickery to get the speed up (certainly a possibility).
I suppose if you bumped the serial speed of the USB/FTDI connection on the Arduino, and wrote some really tight code on both ends to parse things as fast as possible, you might be able to get a decent frame rate (10fps or so). The thing with the original QuickCam, though, was the fact that it only had 16 shades of grey at 320x200 resolution - so it was only needing to push 32000 bytes per frame (roughly, not counting overhead).
If you could get the raw pixel data from the camera, it might be possible to send a stream of pixel data values, perhaps with inter-frame pixel difference values (and key values every so often) to keep the data rate down, perhaps a small buffer with simple RLE to further lower the data rate (or some other on-the-fly, per scan line compression scheme)...