I'm surprised you don't have issues with people using Bluetooth, wireless headphones and other devices on 2.4GHz, or setting up their own APs. There was an Apple demo a few years back where they had to ask everyone to turn off AP mode on their phones because they were killing the demo wifi with 200+ networks in a room. People just turn it on and forget to turn it off.
I don't know how we can ever get devices to really share the 2.4GHz space now. In crowded areas with lots of mixed devices owned by different people no amount of individual management is going to help. Where I live a lot of bandwidth on 2.4GHz is wasted just by old 802.11b and g beacon packets. Routers provided by ISPs, with the TX power turned up to 11 and 802.11b mode enabled in case the customer has an old Nintendo DS or something.
What we need is a new band just for wifi, heavy regulated and with a new protocol that shares nicely and does away with bandwidth wasting crap like beacons. Much smaller channels and many more of them, non-overlapping, lower bandwidth but with the ability to bond when bandwidth is available and won't kill the base rate for everyone. Some solution to the hidden transmitter problem would be nice too, like maybe a mesh network protocol for reporting conflicts.