My grandparents lived in a neighborhood very close to the Philadelphia International Airport. About 20 years ago, everybody's garage doors started randomly opening themselves. It turned out that some navigational radio frequencies from aircraft and towers were bleeding into the openers' range. There's a lot of this, like wireless land-line based phones sharing spectrum space with wireless network interfaces. Sometimes I wonder if there's anybody paying attention at the FCC.
Edit - Added: There's a nice toy at
www.thinkgeek.com called the ninja remote. It's a small remote that scans through multiple code sets until it finds one that works on a device. Then you have a remote on your keychain for the tv/stereo/cable box... Lots of fun. (Mrs Neo dropped one in my stocking a few years back)