When setting up a wireless network at home, I was surprised to be able to connect to my neighbor's unsecured wireless router. Not only could I have used his bandwidth for free, but had I been so inclined, I could have used the connection for illegal activities. If the police came looking, he may not have been able to prove the activity didn't come from one of his computers. Properly securing wireless is not hard. Look in the manual for changing the SSID to something unique, turning on WPA (avoid WEP) for authentication and TKIP for encryption, and using MAC address filtering.