This didn't happen to me, but a guy I used to work with:
He was a netadmin for an industrial molded plastic company. He was giving a tour of the LAN room to some of his friends. "Look at my new hot-swappable RAID!" he said, indicating the main production and engineering server. He then popped a drive out. His friends gasped. He laughed and re-inserted it. The server shut off and would not boot back up. When he re-inserted the hard drive, it was not lined up correctly and it disconnected the backplane from the rest of the drives. He had to re-initialize the array and restore all data from backup. Took about 20 hours straight.
Several years later, this same guy put extra RAM into an older Dell server (during the middle of the day). He kept rebooting and rebooting because there was an error message about the size of the memory being misreported or changed. Finally he turned extremely red in the face, picked up the server, ran out of the server room, down the hall, and into his cubicle. "What did ya'll do to my server?!" he yelled as he ran past. After 5 minutes of Dell tech support, he ran EISA config and let it update the memory settings. I watched the whole thing. It was hilarious. In retrospect, I don't think the rest the company thought it was hilarious when their e-mail was down for that period of time!