Take two Macs running Screen Sharing and someone who couldn't be bothered to cross the office to put a laptop to sleep and this is what happens. I'd been scanning some notebook pages to park in DevonThink. Because the laptop was physically closer to the scanner/printer, I used Screen Sharing from the laptop to control the scanner-management software that I had running on the desktop machine.
Once I got back to the desktop I thought it would be an idea to put the laptop to sleep. Although it is matter of metres away I decided on the lazy option of just going into the laptop through Screen Sharing from the desktop machine. As the screen painted, I realised my fundamental error. Hello Infinite Loop.
Well, it took a few moments to fill in the image as bits of screen data whizzed from one machine to the other. And, not surprisingly everything got a little sluggish. Keystrokes certainly didn't work. I'm not sure whether that was because of the cycles Screen Sharing was chewing up or because the keystrokes were flying backwards and forwards over the network to see which machine really owned them. I had to grab a camera to take this picture then just shut the lid on the MacBook Pro to cut the feedback loop.
Remember, don't try this at home, kids.