Almost all of those non-AP networks you see (usually with that name, and never with a route to the internet or dhcp) are due to a pernicious <i>Thyphoid Mary</i> behavior in Windows' wireless networking UI.<p>In at least Windows XP, if you <i>ever</i> join a "computer-to-computer" network, your computer will advertise that network (or the last such network) whenever it is not connected to another SSID, in perpetuity. Airports are the primary breeding ground for this disease.