http://www.nytimes.com/interactive/2012/05/23/business/How-Google-Collected-Data-From-Wi-Fi-Networks.html
May 23, 2012
How Google Collected Data From Wi-Fi Networks
While taking pictures for its Street View project, Google also recorded Internet traffic from open Wi-Fi networks in homes and businesses. To capture the images and the data, Google used cars equipped with roof-mounted cameras and computer hardware.
By RITCHIE S. KING and MIKA GRONDAHL
Sources: Federal Communications Commission; Verizon Wireless; Sam Madden, computer scientist at Massachusetts Institute of Technology