1) "What happens to the innocent drivee, victim of a war driver, when the cops burst in and arrest him because his ISP's records show him downloading child porn and instructions for blowing up bridges, gassing subways and wearing white after Labor Day?" Unless they find evidence of the kiddy porn or whatever on the actual computer, traffic to that network will not incriminate you.
2) Most people pay a fixed fee for bandwidth, so sharing their wifi is not a big deal. If they do not pay a flat fee, it's their responsibility to secure their network. If you crack their protected network AND they don't pay a fixed fee, that could possibly be considered theft of service.
3) "your intention on "wardriving" is to steal internet access it all boils down to that." Well you answered it: "would you do this just for laughs and giggles" Yes, and research, and sheer curiosity. Some people, myself included, would like to know how much wifi is around their city. It's fun. when I have kismac running, I rarely think of whether I'm going to actually use the wifi - it's just fun to know that it's there.