The FAQ and info on https://openwireless.org/ doesn't seem to address security and privacy from the "guest user" point of view. They do have a link at the top "Using a network named "openwireless.org"? Check out important information about this network." which provides information for a guest user - but only mentions about being considerate and not abusing the service.
How does a user establish trust with each Open Wireless access point in order to determine it is not a rogue/fake AP? How are potential guest users being educated, besides a mention of HTTPS Everywhere? (Which most potential guest users don't really understand, and can also easily be manipulated into overriding SSL security warnings, such as one that may come up if the guest is being routed through a mitm SSL proxy.)
If this does become more widespread, I could definitely see a lot of money to be made for "Open Wireless VPN proxy" subscription services. But if the point is to "help change the way people and businesses think about Internet service" then shouldn't the guest user security issues be in the forefront with at least as much important as the host?