• Treat others as you would have them treat you. If you've ever used someone else's wifi, you should also share your own.
• Put productivity before profits. Restricting access to the internet can mean big profits for a small group of people, but everyone pays through loss of productivity and access.
• Allow easy access to the internet. More and more, access to the internet means access to speech. If people do not have access, their voice cannot be heard.
• Use open wifi without guilt Use open wifi knowing that you are also a contributing member, sharing your own wifi. The Ultimate Open Wifi User Kit makes it easier.
• Give and Take This idea is based on the gift economy, where people who can give do so, and people who need receive. The roles reverse from time to time, but the key is it about sharing.

Yes. There are precautions you should be taking already to protect your data.

Yes! You can give your connection priority over others. Set-up correctly, you can run a free wireless node and never notice a change in your speed - even when others are using your network. Configuring Your Router

Regarding using and sharing open wifi, there are some clear parts of the law but mostly it is relatively grey area because there are few specific laws or court decisions about open wifi in particular. In a sense, we're defining the law through our practices. On this site, you can find more about Open Wifi and the Law

• Steal This Wi-Fi by Bruce Schneier on the Wired Magazine Security Matters blog 01.10.08
• Put Wind Powered Wifi on your Roof