You've got an Apple AirPort wireless network base station, and a mix of Macs and PCs (Windows or Linux) in the house. When you first turn it on, it works great with all of your computers. You hear about people who drive around and find open wireless Internet connections like yours and think it's neat how we can all share. Then you read that the Department of Homeland Security considers open wireless networks a security threat, and you decide to enable that "WEP" thing in the AirPort Admin Utility. (You find out later that WEP doesn't stop the determined, but at least it keeps your neighbor from using your connection the way you can use his.)

Then you realize that, while your Macs are still gleefully wireless, your PCs can no longer communicate. After weeks of groping the web for other people having the same problem, you stumble across this Seattle Times article all about the problem and its simple solution. And your sanity returns.

By the way, WarChalking.org reports that the King County Library System (Seattle) is installing open wireless Internet access in many of its branches. No encryption or passwords needed.

It's difficult to know how paranoid to be about open, shared Internet connections. All traffic is visible to anyone on the same sub-net, and unencrypted traffic (like regular web browsing and even many email readers) can be seen and possibly exploited right away. Encrypted traffic, like web shopping or banking transactions, though obscured, can still be recorded, and if a flaw is ever found in the encryption scheme, or computers just get fast enough to crack it, or enough time passes to crack it, nefarious spies may be able to open and exploit old encrypted recordings. But this is going to be theoretically true no matter how good the encryption is.

In general, if your data (encrypted or otherwise) is good enough to be transmitted over the Internet, it's probably good enough to fly through the air. Landlines do give you some security, but your credit card number goes through many computers before getting to Ticketmaster-- and you're more likely to get your number stolen by a Ticketmaster employee than a 'net snoop, anyway.