Google collected unprotected wifi data while taking Street View pictures between 2007 and 2010, and paid $7 million fine to the FTC. In a class action lawsuit on appeal Google claimed that it did nothing wrong and Computerworld reported Google's argued:

...that its data collection did not violate the Wiretap Act because it fell under an exemption that makes it lawful to intercept electronic communications that are readily accessible to the general public.

However on September 10, 2013 US 9th Circuit Court Judge Jay S. Bybee wrote in an opinion opposing Google:

Even if it is commonplace for members of the general public to connect to a neighbor's unencrypted Wi-Fi network, members of the general public do not typically mistakenly intercept, store, and decode data transmitted by other devices on the network.

Now the case against Google will go to a trial court, so this is a long way from over.