I really wish some service (such as Fon) would provide a vpn service that I could setup and automatically route all guest traffic through. This way Fon could establish themselves as an ISP, and be protected legally (common carrier), and I wouldn't have to worry about what people are doing with my wifi.

I've also though about setting up a guest network that routes over Tor. This way none of the traffic could be traced back to me.

Basically, I would love to provide free wifi for neighbors to use that is limited to a few mbps, but I don't want to have to deal with the legal risks associated with this.