Biological weapons:
Any society member found to be mailing powder of any type to their victims will be removed from the society, whils it is an interesting idea,
a) you won't have any idea they've opened it intill they've phoned the police to say they've recieved mysterious powder and a note saying 'you're dead' and
b) the uni will come down on you like a tone of brinks for creating anthrax scares.