Lee, Timothy, B. "Sniffing Open Wifi Networks is Not Wiretapping, Judge Says." ars technica, September 7, 2012.
From the article: "A federal judge in Illinois has ruled that intercepting traffic on unencrypted WiFi networks is not wiretapping. The decision runs counter to a 2011 decision that suggested Google may have violated the law when its Street View cars intercepted fragments of traffic from open WiFi networks around the country. " Read more
See also
Kerr, Orin. "District Court Rules that the Wiretap Act Does Not Prohibit Intercepting Unencrypted Wireless Communications." Volokh Conspiracy, September 6, 2012.
Kerr, Orin. "District Court Rules that the Wiretap Act Does Not Prohibit Intercepting Unencrypted Wireless Communications." Volokh Conspiracy, September 6, 2012.