Gizmodo has this brilliant post. And if you are one of the bluetooth crazy people, then you are screwed.

bq. Alberto Escalarte of CacheOp alerts us to the new practice of “bluejacking,” which involves using Bluetooth to surreptitiously send messages to strangers:[U]sing a phone with Bluetooth, you can create a phonebook contact and write a message, eg. ‘Hello, you’ve been bluejacked’, in the ‘Name’ field. Then you can search for other phones with Bluetooth and send that phonebook contact to them. On their phone, a message will popup saying “‘Hello, you’ve been bluejacked’ has just been received by Bluetooth” or something along those lines.