Stuff is stuff. Bandwidth is bandwidth. Bandwidth is not "stuff". There are established conventions about where outdoors ends and your residence begins. Not so with bandwidth!
If you put an unsecured WiFi net on the air, how is someone to know (to the precision of criminal law, at any rate) whether you are offering free beer or just forgot (as in the current case)?
Obviously, even if you are Panera or Whole Foods or that silly coffee outfit, you ought to be practicing proper network hygiene! You should make sure your customers' mag stripes go over a separate, secure network.
Public policy should not reward failure to secure networks. If you put it out there, it's free! And if someone utters a threat against the POTUS over your network, well, you do have your MAC address logs linked to your video surveillance, don't you? MAC addresses? Video? Time stamps? Sure, we've got all that. But, oh, well he might have been parked in the alley behind the dumpster .. our cameras don't cover that area ... and, of course, it's all academic, because the perp changed his MAC address before accessing the network, so our logs are worthless!
But I'm not advocating legislation. Free WiFi is valuable. It should remain unregulated and be kept as unlawyered as possible. Regulating it would make it more expensive. And, as I said, I'm cheap. Especially when it comes to lawyers and regulation. It's in my personal selfish interest, thank you very much!
You are very naive in this area. Someone is paying for that "bandwidth". Unless the person advertises that the bandwidth is freely available to all/any, it is "owned" by the person who contracted for it and is paying for it. 99.999% of all DSL/Cable contracts FORBID you from sharing your bandwidth with the neighbors. "Gee, I thought by them not securing their lawnmower and leaving it on the front lawn, they were giving it away to anyone who walked by..." won't fly in court and neither will "Gee, I thought I could just use my neighbors wireless without their permission and steal bandwidth they are paying pay" won't fly either. Theft of services.