From CaptainWalrus on the Bukkit forums:

Is there a way to make it so if a player drops an item, there's a 50% chance the item will disappear, pretty much just obliterate in the air xD And have it broadcast a message to the player > ("Your item has become contaminated, it's no longer good!")

An itemdrop trigger could be interesting - will look into this after the current betas are stable and released.