Several years ago, it was new laptop day at the startup I worked for. We didn't have an office as much as a coworking space. When people went to lunch, they just left their new MBAs on this big communal table. Some shut the lid, some didn't even lock the screen but those would've been taken care of in ~5min.
Anyway, I may or may not have switched some laptops around but the point is someone definitely did. Half an hour later people returned. Some of them were instantly confused. Some of them entered a wrong password a couple of times. Some of them were greeted by an unfamiliar Google Chrome window.
I may or may not have wasted a collective forty or so man-minutes in the span of five but I definitely enjoyed watching the confusion unfold.