Official Google Blog: Nine days ago the data protection authority (DPA) in Hamburg, Germany asked to audit the WiFi data that our Street View cars collect for use in location-based products like Google Maps for mobile, which enables people to find local restaurants or get directions. His request prompted us to re-examine everything we have been collecting, and during our review we discovered that a statement made in a blog post on April 27 was incorrect.
In that blog post, and in a technical note sent to data protection authorities the same day, we said that while Google did collect publicly broadcast SSID information (the WiFi network name) and MAC addresses (the unique number given to a device like a WiFi router) using Street View cars, we did not collect payload data (information sent over the network). But it’s now clear that we have been mistakenly collecting samples of payload data from open (i.e. non-password-protected) WiFi networks, even though we never used that data in any Google products.