Just wanted to put my $0.02 in...
First off, this guy wasn't wardriving. Wardriving is the act of driving around and mapping out access points. Wardrivers normally don't access these networks, they just map out where they are and post them on the web. It comes from the word wardialing where computer's called huge lists of phone numbers looking for accessible computer systems and recorded those numbers. This guy wasn't wardriving, he was sitting in a parked car accessing this guy's wireless network for a long period of time - the guy kept looking out his window and saw this suspicious looking man in his car with a laptop. Now if I kept seeing a guy sitting outside my home, I would get a little pissed too. So, he did what anyone would do - call the cops. In the US, it is illegal to access ANY communication network without first getting permission. That's the law and that's exactly what he was doing. If they find spam sending software, viruses/worms/trojans, or kiddy porn on his system I think they should throw the book at him. If all he was doing was checking his email, then they can be a bit more lenient. However, if you ask me, sitting in a residential area was just asking for trouble. He should of just drove to a business district, or a coffee house, and avoid this situation all together.