Long ago this one (close to 2000), but we were hosting some of our clients on machines in our office because it was (a lot) cheaper for our startup to do so. We

Long ago this one (close to 2000), but we were hosting some of our clients on machines in our office because it was (a lot) cheaper for our startup to do so. We had 3 rather large (for our company) clients running at the time in the server room in the office. The servers where hooked up to 2nd hand APCs so power failures went unnoticed if they were short. One Friday afternoon, we had some drinks (tgif) and a bunch of us (I was the cto....) were fooling around in one of the rooms throwing tennis balls; I threw one straight into the firealarm. This was just a glass with a button behind it: if you pressed the glass it would trigger for the entire (20 story) building. This cut the power and switched on the emergency lights. There was no fire obviously, but, for bureaucracy rules, the firebrigade had to pull up, inspect the building, we had to sign docs etc and then they switched off the alarm and on the power. Too late for our APCs: everything was down and (like said: long time ago for Linux etc) we had to run fsck and basically spent a large portion of the evening getting it all back. We moved to xs4all co location after that incident...