How do you ninja guild bank in WOW

You go in and take everything out of the guild bank then leave right that moment. This is however a very asocial act to perform, and will ruin your reputation.

Recently, Blizzard has added guild bank theft to the list of offenses they are especially keen on, and many former guild bank ninjas have had their items taken, gold removed and all items restored to the guild bank. In one case, a person who had spent all the money even had their epic flying skill removed to pay the difference.