I don't think Wardriving in and out of itself is really illegal. Let's think of what you're doing.
You're walking around with a computer, or driving around, and making a log of the signals you're picking up.
This, to me, is the same as walking around and marking down the color of each house or building you walk past, and including the address of that house (say if you're logging GPS coordinates for the WiFi)
You're simply making a log of what's in the air. It's out there, there's nothing wrong with that. You can even listen to satellite signals legally, as long as you don't break the encryption. (If it's an encrypted signal)
Now.. if you ACCESS the networks that you find, THAT, is where you become illegal. Theft of service.
Just because you're noting what service is where, doesn't mean you're doing anything wrong. It doesn't really analogize with the 'Using a scanner to listen in to conversations' because you're not 'listening in' on sessions that're occuring on those people's access points.
At least that's my opinion.