I understand the law, I just don't agree with it.

Personally, I view the combination of absolutely no security on the AP, and the AP offering its services as being authorized. Similar to being authorized to come in my house if I have the door wide open (no security) and invite you in when you walk by (SSID broadcasts).
I know the difference is technical and not everyone is going to understand how to configure an AP, but that's why they should read the manual, or listen to warnings they get when configuring or connecting to their AP.
So instead of trying to "steal" or borrow in your case, their network why don't you knock on there door and try to educate them.
I don't view it as stealing or malicious because they are offering a service. And it's not borrowing because they aren't getting it back (they probably wouldn't even notice it missing). It's simply using a service they offered. If someone chooses not to shred their trash and they leave it in a public place like on their curb, it's their own fault if someone takes their trash and goes through it. If someone uses the trash for illegal purposes, or by passes security such as even the most insecure lock in the world to get to the trash or ignores a no trespassing sign, THEN that's a crime. If someone is broadcasting use of their open wifi to the world, it should be their own fault for not enabling any security and ignoring warnings that it's not secure.
Offering a service? A service has to be advertised as a service which was post before. So no its not a service.
"And it's not borrowing because they aren't getting it back (they probably wouldn't even notice it missing)." Jelly beans at the candy store are small and the owner would not miss if 10 or 15 were missing, so it makes it right to take 10 to 15 because he would not notice? See this thing called "morals" tells me its wrong.
" If someone chooses not to shred their trash and they leave it in a public place like on their curb, it's their own fault if someone takes their trash and goes through it. If someone uses the trash for illegal purposes, or by passes security such as even the most insecure lock in the world to get to the trash or ignores a no trespassing sign, THEN that's a crime." And if you check with the ISP they will tell you the same thing about using another persons internet

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"If someone is broadcasting use of their open wifi to the world, it should be their own fault for not enabling any security and ignoring warnings that it's not secure." Like I stated before they might not understand and it takes "ethical people" to help them out.
Like I've said, there is also the analogy of someone creating a private web page on a website and choosing not to protect it at all and ignoring warnings. Then the person who sees it advertised (indexed) in google, who has no malicious intentions, and clicks the link and that person should go to jail? Nope. It's the sites owner's fault for negligence. Even though Apache defaults to making the web page public just like an AP might, even though the site owner has no idea what they're doing, it's still the owner's fault for not making any effort to limit access.
I never used an open access point. I've never even owned a smartphone. I'm about to get a wifi card for my desktop though to test my own wifi security and was hoping to also use it for open wifi networks. Kind of bummed the last part is considered illegal.
Yes I know people can read the manual but there are "baby boomers" and "Gen X" people that these manuals make no sense to. With knowledge comes responsibility, so instead of doing something malicious help these people out.
That's the thing though, it's not a matter of tech savvy people taking advantage of those who aren't. There are way more people who don't understand technology than geeks, so I'm sure there are more computer illiterate people breaking this law than geeks breaking it. But yes I have thought about yesterday and today of notifying people who may of accidentally have setup open wifi...
You should do more then think about it, you should do it.