We used to have food thieves at - well, a few jobs I've had, but I was surprised when we had them at a job I had in an upscale office. People would take things out of containers that had names, everything. One co-worker went to get her lunch, fried chicken, and someone had eaten half of the chicken and left the BONES in there.
And another time someone ransacked my lunch, took stuff randomly out of different ziplock bags, and just left them open. It sucked.