One of the most popular posts at FiveCentNickel’s blog  is the one title “Piggybacking on Your Neighbor’s WiFi .” Just a few days ago someone brought up the point of legal responsibility of your network and it led me to do some research on the topic. According to most, if someone connected to your wireless network, performed an illegal act, the trail would lead directly to you. While you ultimately will be exonerated, if you are innocent, it is going to be a headache for you for a very very long time.
When the authorities start tracing back to find the perpetrator of a crime, the electronic breadcrumbs will lead back to your house. If the crime is serious enough they’ll come crashing in and arrest you, waiting until later to ask any questions. Then, proving you’re innocent is difficult because your typical home user who doesn’t encrypt his or her wireless network isn’t going to keep network logs of who is connecting to the network and what they’re doing.
If left unencrypted, anyone could walk up to your house, connect to the network, and fire off a virus and all the authorities would find is your IP address at the end of the trail.
Nickel brought up the benign and moderately inconvenient reasons why you should encrypt your wireless (you lose bandwidth) but I think the more serious doomsday scenario reasons (one in a million chance) are worth mentioning.