It looks like the original O'Reilly post was a bit imprecise. On one hand, it says "your iPhone, and your 3G iPad, is regularly recording the position of your

It looks like the original O'Reilly post was a bit imprecise. On one hand, it says "your iPhone, and your 3G iPad, is regularly recording the position of your device into a hidden file." Later on, it mentions a "a list of hundreds of thousands of wireless access points that my iPhone has been in range of". This suggests that the list is one of cell towers (and perhaps Wi-Fi routers ?), but not actual device locations.