I knew a guy who took down the entire ATM network on the East Coast of the USA for a major bank because he was careless.
On the same team, another guy took down about 15,000 voice mail accounts in Charlotte, NC for the same bank, one of them was the CEO of the bank.
There was some major butts grabbing seat cushions over those 2 incidents, fortunately both were quickly recovered from and no one lost their jobs, it was close, both times it was good people being careless.
TOO MANY PEOPLE believe Computers are INVINCIBLE