The data is only given away the first time a person joins a Karma hot spot. They only get one credit of the 100 MB, and you can only get one credit for them even if they connect to you every day. They only get one credit even if they connect to a different hot spot every day. So for it to be free for you, you need to constantly find new people to join if you bought the hotspot.

Their goal obviously is to let people sample the 100 MB, and then convince them to buy additional time so they can connect once they use up the 100 MB. I can see that working for the person who bought the hotspot, but not really for the people connecting. The last thing I want to do is drop $14 to finish watching a movie at the airport and have the guy who owns the hotspot shut it down in the middle to get their plane .

I can just see people finding them (they see your facebook name and picture when they connect) and begging them to please, just ten more minutes, please.

They are in essence spending $2 for each new customer they hope to convert. My guess is that's the main reason they are using facebook for the authentication, they know most people won't keep setting up fake facebook accounts to get free 100 MB blocks of data, but would certainly set up fake regular accounts if all they were asking for was an e-mail and password.