In a recent article in Technology Review called, The Internet Amenity, Simson Garfinkel says that wireless Internet service is cheap (no wires to run, not a lot of central equipment). What makes it expensive for a business to provide is the overhead--credit-card billing, technical support, security.

Open community wireless networks don't needs these services and some organizations (schools, universities, businesses) have decided it's easier, friendlier, and possibly cheaper in the long run to have an open network.