There are pros and cons to both. At my previous job I had an office and felt that it took a lot of extra inertia to get a technical conversation going between people as you felt like you were invading their private space in order to talk. While this barrier to entry has been removed with the open floor plan I think it can easily swing too far in the other direction if safeguards are not added. I can no longer get 30 minutes to actually concentrate on coding without getting an interruption from others on my team.