Steve Jobs guided the design of the Pixar building. Here's a quote from Brad Bird (director of The Incredibles, Ratatouille):

"Then there's our building. Steve Jobs basically designed this building. In the center, he created this big atrium area, which seems initially like a waste of space. The reason he did it was that everybody goes off and works in their individual areas. People who work on software code are here, people who animate are there, and people who do designs are over there. Steve put the mailboxes, the meetings rooms, the cafeteria, and, most insidiously and brilliantly, the bathrooms in the center--which initially drove us crazy--so that you run into everybody during the course of a day. [Jobs] realized that when people run into each other, when they make eye contact, things happen. So he made it impossible for you not to run into the rest of the company."

Edit: here's the source article, although you'd have to register to read the whole thing: http://www.mckinseyquarterly.com/innovation_lessons_from_pix...

I mentioned this in another comment, but the guys from Peopleware did exactly that:

http://www.amazon.com/Peopleware-Productive-Projects-Teams-S...

The also conclude that small offices with 2-4 people and a door that can close is best.