Over the past 2 weeks, i've had things "stolen" from the fridges. Mainly milk, which is bloody annoying. You can only report it to a manager, whom sends an email out. Never will catch the bugger unless i sit in the rest area all day, it's like looking for a needle in a haystack.
Should spike it like i did with my sandwich once, laced it with habinero chilli. Soon discovered whom was eating it when i found it was missing.