You should take a look at this article [link no longer available] if you operate a home or small business wireless network. It details how easy it is to crack the encryption, which then gives the hacker access to all your computer files. What is even more alarming is how many people don't configure the low cost wireless routers correctly and often leave the encryption turned off completely.
A neighbor who uses one of the devices related the story of an individual in a pickup truck who started parking near his home in the evenings for an hour or two. Thinking it might be a burglar casing the home for a later break in, he was understandably concerned. The first thing he did was take a casual stroll one evening when the truck was parked out there, and noticed the guy was tapping away on a laptop. The lightbulb went on, he ran home, and checked his wireless router. Sure enough, he had left the encryption off, and the visitor had been enjoying free broadband every evening.
So the neighbor turned encryption back on, then walked over to the window. Sure enough, within a minute, the guy closed the lid on his laptop, started his truck, and drove away. He has not been back since.
Another friend, who installs Ethernet cabling for a living, related the story of moving to a new neighborhood. After unpacking his laptop and firing it up, he checked for WiFi signals. From inside his home, he was able to see four unsecured WiFi networks from his new neighbors, meaning that none of them had security turned on. Had he wanted to, he could have made copies of their files or looked for personal information.
If you are using WiFi at home, be careful. Turn on encryption and require password access. And if you are operating a home-based business, I can't recommend using WiFi at all. Spend the money to get Ethernet cable to the rooms where you work. One big benefit of cabled networks--much faster network speeds, which is great for doing backups, file sharing, and room to room music sharing.