In some jursidictions, it's also against the law to give legal advice without a law license, but I doubt you need to worry.

As for the accuracy of your legal advice, I doubt it's true everywhere that this forum reaches and even where it is illegal I doubt it is often enforced absent aggravating circumstances. I do know Steve Jobs practically advocated piggybacking when he was touting the original iPhone and its ability to seamlessly flip between the Edge service and nearby, faster wi-fi signals. I hope he doesn't get arrested somewhere for aiding and abetting a felony.

I realize there have been some prosecutions related to piggybacking and I realize there are some fanatics who get very upset about anything that is even remotely questionable from a moral standpoint, but a little common sense usually wins out in the end. In the meantime, I am not going to worry too much about my moral or legal position -- or my contract terms with T-Mobile -- when I surf the Web by my pool using my unsecured wi-fi. And if it fades out I may tap my next door neighbor's unsecured wi-fi or look over the wall and see if he's using mine. Of course that would be invasion of privacy.