Bandwidth isn't the bottleneck really, it's the half duplex nature of 802.11b (nstream cures this).
You have to treat an AP as a conventional class 1/11 repeater, you wouldn't throw too many people on a single segment, most cases you'd limit each segment to 12 seats. This is not exactly correct as a repeater is using CSMA/CD, and an AP is using CSMA/CA, so it would be like a hybrid ethernet/tokenring network as the AP can poll clients if they reach set thresholds.
Another thing that tends to nail wireless is small packets, if you have a client throwing >100packets/sec at the AP and maybe consuming less than 10kB/sec, they're still going to cause the AP to struggle with the load. So having lots of clients giving out the occational burst of small packets can tie things up a bit. Unless you're using 'packet packing' between MTRouters etc.
Anyway, to answer the question the most amount of clients I have on a single AP (single channel) is ~25.
So it's probably better if you have multiple wireless interfaces with sectorised antennas when operating in high density areas.
And for those in Latvia, send some bandwidth down this way!