Here is why you need to secure your WiFi signal

Short story: this guy had an unsecured WiFi hub in his apartment building. Comes home early one day and spots someone sitting in the parking lot with a laptop, using his WiFi to flood the internet with comment spam.

Let me put this clearly: If you don't secure your WiFi, spammers will use your connection to spam with, and if you're unlucky, your ISP will disconnect you for spamming.

Update: Seems that the story itself may spam, intended to attract readers to a site which sells anti-spam products. Read all about it at MetaFilter. The original author has commented to defend his story.

My comments about securing your WiFi still stand.