Truck and Barter

I had never thought to just park the car in the middle of Cameron Station and see if there are wireless signals I could connect to.

Turn off engine.

Turn on computer.

Seven unsecured wireless networks with internet access--including one from Cameron Perks Coffeehouse!

I'm sad to say that the lack of network security doesn't surprise me. But if someone doesn't protect their wireless network, are they implicitly giving permission for anyone to use it? Can an unprotected wireless network owner be held liable for damages that their wireless networks cause to connecting computers, even if others connect without explicit permission?