SAN FRANCISCO

FREE lunch — heck, free breakfast, lunch and dinner, plus all the M&Ms and Red Bull you can stand — is a delicious perk of working in Silicon Valley.

Free or even subsidized food in corporate cafeterias makes eminent sense in such a suburban setting. Corporate campuses, built where fruit and nut trees once stood, are cut off by busy thoroughfares. To go out for lunch, you have to drive a mile or so, park, eat and then high-tail it back to work.

Nothing much, food-wise, has sprouted around those campuses. There is not a bite to eat within a half-mile of Hewlett-Packard’s midcentury modern lab building in Palo Alto, the model of tech campuses in the valley.

So when this cafeteria culture hits the big city, does the collision somehow stultify economic activity? Cities, after all, need people out on the sidewalks.