So, if a user has a laptop on a coffee shop wireless network, access to a log of the MAC addresses registered at the coffee shop could be cross referenced with

So, if a user has a laptop on a coffee shop wireless network, access to a log of the MAC addresses registered at the coffee shop could be cross referenced with Google's data to find out where that MAC address was at the time the street view car went by. If you assume that the street view car happened by that MAC address while that user was at home, you could then look up the residents and figure out the identity of the user of that MAC address. Honestly, it doesn't concern me that much, but I'm trying to figure out what has other people worried.