I would love to see an area talking about this stuff.
A basic service like this would lead to huge growth of open-mesh, perhaps too much.
Personally I am in charge of an internet connection for a group of six small offices we all throw in some cash every month to pay for the connection. If there were a simple mechanism for charging we would probably be inclined to offer free low speed service and paid high speed service in the hopes it would offset our monthly bill. Not exactly altruistic but it would mean cheaper internet for more people in my building and less work for me.