Google and Facebook don't feed their employees because they're naive. At a $65k salary, the meal is fully paid for if you can save employees 20 minutes by having it brought in.
I mean as a new startup to Silicon Valley, not an already established, large company. In the long run, I definitely see how this saves a company money, but for startups where money is tight, I would be wary.
If the company comes out even, is it really saving the employees 20 minutes?