Demends on rate command. Howerver I've seen anywhere from 192-384 kbits/sec PER USER!!!!! (sniffer)
That is 1.536 Mbit - 3.072 Mbit.
Given the small frame sizes and high utilization this is murder for a shared 10 meg ethernet. User performance will definately suffer. If you are totally switched however there is nothing to be concerned about.
Use the quake server as an excuse to upgrade your network
spidey