I know what you're saying, though. If it's open, shouldn't it be okay? Websites are open, and there aren't any laws about using open websites, but it's a little different. If I put up a website, and it's open to the internet, I probably had to take some steps to deliberately open that to the public. There would usually have to be a firewall rule specifically allowing that type of traffic to that specific webserver. If there is to be a domain, a domain would have to be purchased and DNS entries setup. These are things that specifically open the site to the internet, it doesn't usually happen by accident.
With wireless networks, it's different. The average user without any idea of security essentials would bring their new router home, plug it in, and say "it works!" and never change any settings, not knowing that they've created an open network. They're still not giving you permission to access their network, they just don't know any better. That being said, they probably would never know that someone connected, and wouldn't know that an illegal activity is taking place, but that still doesn't make it right for people to take advantage of it.FL Statute 815.06
Whoever willfully, knowingly, and without authorization accesses or causes to be accessed any computer, computer system, or computer network, commits an offense against computer users.
I gave a presentation on WEP cracking recently, and had to know the rules before giving the presentation.