From Bruce Schneier on Steal This Wi-Fi:

Security is always a trade-off. I know people who rarely lock their front door, who drive in the rain (and, while using a cellphone) and who talk to strangers. In my opinion, securing my wireless network isn’t worth it. And I appreciate everyone else who keeps an open wireless network, including all the coffee shops, bars and libraries I have visited in the past, the Dayton International Airport where I started writing this and the Four Points Sheraton where I finished. You all make the world a better place.

ceo