Well, it's certainly "wrong", and I think it's easily justifiable as illegal, and cause for civil actions, though it's still a fairly minor offense.
The main arguments I hear are:
"It's like a shade tree (etc.), the owner loses nothing by my use of it".
No, it's not really like a shade tree. If my shade tree also shades your backyard, and you go sit there, you're not precluding me from enjoying that shade in my backyard, nor diminishing the shade I enjoy. On the other hand, when you're using my wireless network to access my internet connection, you're using up part of two finite resources, namely the bandwidth of my wireless network, and (more importantly, as it's more likely to be a limiting factor) the bandwidth of my internet connection (dsl, cable modem, etc.) While you're using my internet connection, my download speeds on my internet connection are lower than they would otherwise be, I'm only getting partial use of the service that I paid for (and you did not).
I pay Vonage for voice over IP service, and I know that when there's internet activity on my dsl link, I get drops on my voice calls. If you're parked in front of my house, using my DSL connection, you could be screwing up my phone calls, and you'd have no way of knowing whether I'm using that service at the moment or not (no, that traffic doesn't go over the wireless network, so it's not like you can say "well, I can tell there's no activity on the wireless network, so I know you're not using it right now").
"If the network isn't protected, it's an invitation for anybody to use it".
This statement is true in the way that we might say "leaving your laptop on the back seat of your car, in plain view, is an 'invitation' to crime". We don't really mean "invitation" like we might invite somebody to a backyard barbecue, we mean that we're being naive and careless and that some evil-doer may take advantage of us because of this.
When we try to justify our use of an unprotected network, we're not sincere in saying "that's an invitation to public use", we're really saying "that person is so stupid, that they deserve to be taken advantage of as a punishment for their carelessness". This is the way we might say a pilot "deserved to die" when he does something really stupid. Almost a Darwinian sort of justification. If somebody was really broadcasting an invitation, maybe they could advertise this intent through the network name ("all-are-welcome"). Obviously, the typical user has an unprotected network due to naivety, and not a spirit of generosity.
In any case, many of us seem to confuse "acceptable behavior" with "I can get away with it". There's really just something miswired in a lot of brains, whereby an inability to get caught, or a lack of repercussions, somehow makes it "okay to do".
"Well, if I'm not supposed to use it, then don't let it enter my house."
Well, this is a really disingenuous argument, sort of replacing common sense judgement of right and wrong with legal "loophole" mentality. But do consider that you're not just using the person's wireless network, you're using this as a ramp to access their DSL/cable-modem connection, and this resource isn't located in your house.
-harry
