Well micro transactions are perfect for a MeshNet, but how will they implement the liability? When you sign a contract with your service provider, you are responsible for the activity on that service. If someone tap into your service and use it for illegal actions, who would be held responsible for their actions?
When you link onto a Free Wifi network now, it needs some authentication for you to use it, so you are still identified on their network. It's a interesting concept, but it still needs some brainstorming. I do not want to go to jail for someone doing #@%$ on my service.
Breaking your contract with your ISP is an entirely different thing than breaking the law and going to jail. If you see illegal things, then either report it or don't. Just don't knowingly facilitate and you should be good.