Or maybe "oh here's a door. I wonder if it's locked. Newp. Well then, I guess I better go inside, take some photos and read some of their documents. And then use that information for presumably commercial purposes. It's got to be legal and right, the door was unlocked."
Why do people keep using that flawed analogy, Google didn't open any doors, not even unlocked ones, the Wifi signals were broadcast in the clear for all to hear -- including bad guys. They captured only plaintext, they didn't break any encryption, not even WEP.
What Google did is more akin to photographing the contents of the papers you left sitting on your desk... which you left sitting out on the sidewalk for all to see. If you didn't want other people to see your private documents, you shouldn't have left them sitting out on the sidewalk.