Wireless networks are tricky to deal with because, even if they are secured with a preshared key, they do a poor job of providing non repudiation to the network’s owner. It is extremely easy for someone to crack a WEP key (and many times it is easy to crack a WPA1/WPA2 preshared key as well, provided the password is a dictionary-based.) Once this is finished, the attacker can use the wireless network as a digital beachhead of sorts, and launch further attacks. If forensics experts ever get involved, the trail leads back to the wireless network itself. By then, the attacking node has moved on and long gone. Always remember that its trivial for anyone to learn how to hack WiFi.
Would I connect to an unsecured wireless network? Or, would I use a neighbor’s unsecured WiFi? I have done this in the past, but I do not any longer. Honestly, my reasoning is not so much for moral reasons but rather my own self-preservation. Personally, I feel that the responsibility is on the WiFi owner to secure their network. (Breaking an encrypted network is a different story altogether, and one that I do hold a moral compass for.) There are countless open source tools that allow an attacker to sniff, redirect, and modify in transit data as it goes across the air. Weaponized programs such as sslstrip allow someone with minimal computer skills to strip out the SSL encryption used in banking, email, and social networking login forms. Thus, https://gmail.com becomes http://gmail.com, and most laymen don’t pay attention to the address bar the way I do now. Unsecured networks offer no substantial proof that your data will be secure and intact.
What would I do if I found out that someone was using my wireless home network? Firstly, this would not happen because I secure my home WLAN using enterprise encryption (the AES-256 algorithm authenticated to a RADIUS server.) In addition, I use MAC filtering and an IDS in a layered approach to security. (I’m paranoid) However, in the context of the question, if I were to find someone using my WiFi network, I would first set up wireshark or tcpdump and try to determine the user and what they were using the network for. Piggybacking a wireless network to stream Netflix is one thing. Doing the same to download child pornography is something else entirely.
Passing laws policing the internet sets a dangerous precedent. Obviously, we need laws that will punish those that break an encrypted network, but I do not think punishing WiFi network owners is a good idea (even if they chose to leave it open.) A better solution would be to pressure WAP manufactures to implement out-of-the-box WPA2 encryption using a random, alphanumeric password. WAP manufacturers should stop setting default passwords that are the same across an entire product line. Manufactures could also set complexity requirements for the WAP password. This would cut down on the effectiveness of wireless cracking tools like cowpatty or aircrack. You will never eliminate threats such as these entirely. A determined attacker will always find away in (perhaps leveraging some sort of social engineering attack to get the owner to divulge the key) and no system is 100% secure. But passing broad laws is not going to help here. Education, and better product security should be the way forward.