Hi Stone,
There are also USB capture devices like the
GA-VD207 that can do hardware MPEG-1/2/4 compression, thus lightening the CPU load.
There are other advantages to USB webcams that you missed. Decent CMOS based USB webcams usually handle changing light conditions better than equivalently priced composite CCDs. In fact, most of the high quality CCD surveillance cameras have a mechanical iris which opens and closes to adjust to brighter or darker exposures.
On the other hand, CMOS cameras are usually less sensitive to light than CCDs. That's why they generally don't need a mechanical iris to limit the light in bright conditions. But it also means that CCDs will generally produce a better image in low light.
pb