It appears to be a manifestation of a feature of Windows that I wrote about earlier this year. When Windows connects to a network, it retains that network’s name, or SSID, then broadcasts its as an ad hoc network, essentially inviting a connection. You can find more details here. Microsoft has said it will fix this in the next XP service pack; it’s unclear if Windows Vista behaves this way. So why do you see so many of these? My theory: It’s viral, but not a virus! What’s the thing almost everyone wants to find when they open a WiFi-enabled notebook and search for a connection? Why, free public WiFi! If you see that — and you don’t know any better — you connect to it.
Wonderful. I’ll refrain from making any smug Mac fanboy comments.