There are many pages on the web advising the use of wifi channels 1, 6 and 11 only, so that your wifi channels don't overlap.
Obviously this makes sense when you only have your network do deal with, but in most urban areas there are now a plethora of other networks, all using the same channels. In my current location there are about 4 networks on channel 6, and a couple on channel 1.
So my question is: What happens when you get lots of networks on the same channel? Do the intelligently share it? It is better to have two networks on channel 6, or one on channel 5 and one on channel 6?