Link Harvest: The Origin of Fake "Free Public WiFi"
Apparently, it's a Microsoft XP bug the causes you to detect "free public wifi" where there is none.
http://www.techdirt.com/blog/wireless/articles/20101011/03194311357/the-history-of-the-fake-free-public-wifi-you-always-see-at-airports.shtml
http://www.techdirt.com/blog/wireless/articles/20101011/03194311357/the-history-of-the-fake-free-public-wifi-you-always-see-at-airports.shtml