Don't forget the "War on Touror" wherein undercover police officers hand out $1000 fines to college kids after they've asked them to give an impromptu history tour of the peninsula.
I'm not a lawyer, but the police can ask you to perform a crime and bust you for it if "you were inclined to commit the crime anyway" or something like that. The rule of thumb is like if a tourist walked up and asked for a tour, would the suspect do it then? If so a cop can nab you for it.
The sting revolves around Charleston licensing tour guides who must pass a pretty hard test and the rickshaw/bike-taxi operator not having taken/passed that test. Of course there was a recent case in Washington D.C. where the same law regarding tour guides was recently struck down[1], so who knows if he could have fought it. Last I heard the guy who got busted was paying his fine in installments.