Bluejacking is a bluetooth activity that helps to avoid boring times in public places with high bluetooth-device density (e.g. airport terminals, train stations, conferences). Usually, bluejacking involves a lot of human-device interaction that makes it obvious to eventual "victims". An application from blader-software.de is now automating this bluekjacking-procedure. That is really cool ;)
I already tried it on my Nokia 3650. You may download it as freeware from this location.
Bluejacking is not allowing access to secure portions of the attacked device. It is just very annoying for the victims to receive messages all the time.