I once put a 'notice' on the (usually out of order) ATM outside our local Building Society branch. It read:

"Due to circumstances beyond our control, this ATM is currently in order and working. We apologise for any convenience this may cause."

It was three hours before the staff, curious as to why all the ATM cusotmers were laughing like drains, finally sent someone out and the sign was removed.

Needless to say, the ATM was out of order again two days later!