Wardriving is: "the act of searching for Wi-Fi wireless networks by a person in a moving vehicle, using a portable computer or PDA." The best known objective is to find an available Wi-Fi network to connect to the Internet.
Another objective is to geo-tag Wi-Fi networks. This has been done on numerous occasions and it resulted in maps that include overlays to Google maps like this map of Seattle.
There are use cases for such maps; for the purpose of law enforcement, it shows where a person is connected to the Internet and for advertisement, it shows where a person is connected to the Internet. On its own, it is a little thing. When you look at it in the context of what has been so brilliantly documented in the Wire, it is part of a technological fight against crime and when you look at it in the context of Google, it is part of the increasingly sophisticated way of serving locally relevant adverts.
Slowly but surely personal privacy becomes less private. People, organisations and organisations can address you because they know where you are. The weather is fine, I may take my bike and without a mobile, you may think I am at home because my laptop will be left turned on... I hope nobody cares, will miss me as a result and get annoyed ...