[michaelvanham]

I can't speak for rffn, but many people want to avoid using the 2.4GHz spectrum due to congestion.

In the 2.4GHz band there is a limited amount of space available, and there are now many wireless routers in typical residential neighbourhoods all competing for the same space. Many other devices such as cordless phones, baby monitors, and wireless speakers also use 2.4GHz and interfere with wifi signals. Most microwaves generate significant amounts of noise in the 2.4 GHz band when in use.

In the 5GHz band there is much more space available, and there are many fewer competing devices and sources of interference. The penalty of 5GHz is slightly less range, and more expensive wifi equipment.

[rffn]

Exactly. Where I live I see about 20 networks in 2.4GHz, not even talking about Bluetooth, 802.15.x and other 2.4GHz users. Over the latter WLAN should have priority though if the other devices are standard conforming. In 5GHz I can still only see one or two other networks.