Might be this guy, trespassing in the building is a lot different than accessing an open network from a public place.

Actually you can enter a building. If they tell you to leave and you don't THAT is when you can be charged.

Door to Door salesmen "trespass' every single day.

Does there exist legal precedent for this? It would seem hard to argue for expectation of privacy on an unsecured wireless network on a protocol without TLS.

Why is that so?

A landline phone is also trivial to tap into. Should you not expect some degree of privacy on the phone?

Phones, like mail, are a special case in a whole bunch of ways, legally, is my (Not A Lawyer) understanding. Using them as a basis for comparison is probably not going to reveal a lot.

Well we were talking about expectations here, were we not? I certainly expect my IM, email, VoIP and other forms of communication to be no less private than phone or post. So does, I believe, nearly everyone else. Just because one stumbles (stumble is not the right word though for what article described - the malicious intent was clear) into an unsecured segment does not make it right to eavesdrop.

Do you not picture a distinction between a landline (non-cordless) phone and wireless internet?

By 'trivial' to tap into, you mean I'd have to physically cut your line somewhere and attach a listening device, right? It seems very reasonable to expect privacy on a physical point to point wire.

With Wifi, if you're my neighbor, I need to sit at home with my computer and your photons come straight to my antenna. It's like you're giving them to me. I don't see the similarities.

If one looks at historic FCC regulation, it was always okay to listen to communications, but not to divulge the contents to 3rd parties. Even with just those older regulations, using data "heard" would be prohibited since that would involve transfer to others. I believe strong protections similar to wiretap laws were added for cell service, but unlicensed gear that has no protection from interference generally doesn't have any. For example in spite of an expectation of privacy, cordless phones are unprotected. Anyway, while there may be room to argue over access to certain communications being permissible, it's clear that one is prohibited from using anything heard (obviously including passwords, credit card info etc.)

The FCC rules for WiFi devices basically state that they must not cause any harmful interference and must accept any interference that occurs including that which may cause undesired operation. Read the manual that comes with any WiFi device and the text of that will be in there (the FCC rules require it to be).

Is that actually also legal to wiretap networks that they own? What about the classic method of setting "Free WiFi" using simple tools and a 3G phone? Does that make it "legal" to wiretap in US, at least?

Well, no police have shown up yet. I'm hoping for the best.

Also, the FCC isn't charging Google for what they did. So I assume I'm fine.