On that one in particular - is there a law against that? I know rules on food service workers taking things home vary quite a bit.
Apparently chocolate cookies had an unfortunate and inexplicable habit of being crushed under other products and being deemed unfit for sale.
Once the policy changed and staff had to throw damaged products in the garbage compactor, apparently a lot less chocolate cookies were getting damaged.
That is to say, a take-home box of food a day shouldn't be a problem on financial grounds, so rules like this are more of a power of ethics issue. In abstract.
However, in most cases (I don't know about facebook in particular) food service workers are contractors, and I'm sure the economics don't sort themselves out that way.
Anyway, facebook leadership could discourage this sort of nitpicky loss control.
One of the remarkable innovations introduced by the Patrician was to make the Thieves’ Guild responsible for theft, with annual budgets, forward planning and, above all, rigid job protection. Thus, in return for an agreed average level of crime per annum, the thieves themselves saw to it that unauthorised crime was met with the full force of Injustice, which was generally a stick with nails in it.