While mucking about with KisMAC on my MacBook today, I saw that there were 27 WiFi networks in my neighborhood (single family homes and quad-homes). All but three networks were encrypted. Less than half of the encrypted networks used WPA, the rest used WEP.

Two of the three unencrypted networks were named "Linksys" (noobs) and the other was an ad-hoc network (looks like a printer).

About half of the networks were pretty weak, and this was via the MacBook's tiny built-in WiFi antenna. Imagine how many networks would be found using a high-gain antenna.