more with the iPhone 2.0 location stuff

Did a little experimenting, and it looks like iPhone 2.0 is using the location of "Wi-Fi" access points to further pinpoint location.  This screenshot shows the same level of accuracy as iPhone 1.x had... I have Wi-Fi turned off here, and it puts me more than a mile away, in the middle of the park:

Now, as soon as I turn Wi-Fi on, the location resolves to nearly perfect accuracy... knowing pretty much exactly where my house is (yeah, it's obviously been years since they updated the satellite photo):

Kind of surprising.  I would expect them to be able to have decent location information around commercially-provided access points, but you would expect that personal residential access points would be another matter.  I wonder if they have people wardriving around towns with a GPS, correlating GPS location to which access points show up?