Here's a great example of creative minds taking advantage of new technology. Those crafty, meddling kids in the United Kingdom have popularized a way to send text messages to unsuspecting owners of Bluetooth-enabled phones and PDAs. The BluejackQ (or "Bluejack You") site, apparently run by a 13 year old English girl, has all the details. Her site has been hammered recently by visitors, but she reports it's weathered the storm. Netcraft reports she's running Apache on Linux, so good for her!
A poorly edited by technically informative Slashdot post describes the underlying mechanics of the system used to send messages. As another Slashdot poster mentions, Bluetooth isn't like the Internet. If you get an unsolicited Bluetooth message, turn around. The sender can't be more than a few dozen yards away!