One thing we’ve learned about modern technology is that there’s no limit to the inventive ways ordinary people can subvert or take advantage of it. Take the Bluetooth radio communication system used in many current mobile phones; this is designed to allow you, for example, to use a wireless, hands-free headset while the phone is safely in your pocket. But any Bluetooth device is capable of talking to any other device over a range of a few metres. A phone with Bluetooth enabled will tell you about any devices nearby that you can communicate with. Mischievous people have started to exploit this by sending cheeky messages to some stranger they see in a public place, usually personalised ones such as “I like your tie”. Most victims will have no idea how the message arrived on their phones, and their startled expressions are reward enough. Fears that the technique might represent a security flaw seem to be unsubstantiated.
A lanky young woman with long brown hair was waiting to take a train at London’s Waterloo Station when she got a surprising message on her mobile phone from a complete stranger. “I like your pink stripey top.” The woman who looked around in confusion had just been “bluejacked” by a 13-year-old British girl named Ellie who goes by the nickname jellyellie.
The International Herald Tribune, 17 Nov. 2003
But why would somebody bluejack a stranger’s phone? The motive behind the craze is to freak out other Bluetooth users that you might encounter in public — for example, a bluejacker will check out other Bluetooth users on the tube and drop them a message that only someone in the same place will appreciate, for example, their choice of newspaper or colour of their top or just a message to let them know that they’ve been bluejacked.
Znet UK, 6 Nov 2003