CNN and Money
apparently feel that connecting to the Internet through a neighbor's wireless network
is an ethical question of great concern.
I have only recently installed a wireless network so that my brother could have broadband while staying at my Mother's house. I did a lot of tuning and messing around to extend coverage, but the only computers that can use my network are those I have granted access to. It was a minor bit of extra work, but I don't have to worry about people "borrowing my bandwidth".
If people leave their networks open they are inviting you to use it. The Wi-Fi systems use a public frequency that is shared with some cordless phones. If you use the frequency, you must make your own provisions for privacy. If you leave the keys in your car with the motor running, don't be shocked if it ends up missing.