I work for a small start-up. We have something like 2,500 square feet of office space, including private offices for most of six people there. We also have no servers (everything is cloud-based) and everyone uses a notebook, wifi, and cell/cordless phones. What tends to happen is that 2/3rd of the floorspace is empty at any given time. We all tend to congregate in the centrally-located conference room. If people need to make a private call or really concentrate on something, they'll steal away to an office and then return later.
This behavior isn't dictated by management, it just happens. I've found out that if I sit in my office for most of the day, I feel out of the loop (even with constant email exchanges). There are some downsides to being constantly plugged-in to everything like that, but overall, I feel it's a net-positive. A great amount of collaboration just emerges.