TL;DR pranking unlocked computers undermines security by providing cover for real breaches and creating a culture of shame that discourages open reporting of security issues.
It's a common rule in companies that employees must lock their device when it is unattended, to prevent people from using your access in unauthorised ways. Screen locking is a common compliance requirement, and a good security practice.
People new to these company environments can take a while to learn the locking behaviour. It's not an intuitive reaction. There was no ancestral selection process. Most people don't take that level of security precautions with their personal laptop. Seasoned people sometimes forget.
Doughnutting is the practice of seeing that a colleague... (read 276 more words →)
Another consideration about schemers is you might not be able to "fire" them or fix them easily, even if you can reliably trigger the behavior.