When I'm careening from one place to another across Silicon Valley, my Powerbook is often hard at work. Using an application called iStumbler (free and Open Source), the Powerbook 'senses' Wi-Fi networks (and Bluetooth, and more) and reports findings such as signal strength and whether the network is secure or open.
Recently, I stopped at a traffic light in front of one of the area's largest high schools and iStumbler stumbled across a HUGE number of open networks. I didn't have the time, nor the inclination, to snoop and find what was on those networks or how much bandwidth could be stolen, but it certainly raised a lot of questions about what students and teachers know about securing wireless networks.
I contacted the school's tech coordinator and we talked about bunches of ways to lessen the security risk. She's working now to let every staff member know how to log into their encrypted network and not inadvertantly broadcast free bandwidth - unless they mean to, of course.
Lesson for the day... grab a Powerbook and sniff your campus. You might be surprised what you find.
