I think we have a real problem with people stealing food out of the station fridge! Although I've never been a "lunch theft" victim, I did spot the following note taped to a TV dinner in the freezer:
"Seriously, BACK AWAY! This is NOT your food! It's $#%&#'s and she will be MAD!"
If you have this problem at work, I think you should invest in one of these! Nothing says "I love working with you guys" quite like locking up a tuna sandwich!