Ad-hoc network. (RTFM and all that. )

Even ignoring the wisdom of entering a random van ad-hoc network promising free candy! free interwebs!, I thought everyone knew about the viral ad-hoc ESSID syndrome: When (certain versions of) Windows lose connection to a managed network, they continually try to join an ad-hoc network of the same ESSID. Other Windows machines see them and display the ESSID, people randomly click on it, and now their machine is broadcasting it, too. "Free Public WiFi" is by far the most common of these.