Fog Creek has pretty obviously done that; it's one of their top priorities. I've worked at companies where lunch is communal and companies where it isn't, and it seems to me that the difference has less to do with personality types and more to do with cohesion.
Put differently, the types of teams who want to eat lunch together are the types of teams you should want to be on. The company shouldn't need to enforce it; they should just help to facilitate it.