It may not be for everyone, but for people like me it really boosts productivity. The last office I worked in was a massive open-office in a warehouse which sounds just miserable, but it was great. If I ever had a question, I could just lean over and ask the person I had a question for. No waiting for emails to bounce back and forth or for people to get back to their IMs. If I needed to make a private phone call, I'd just walk out of the office to do it. Plus, having people around me made it easier to focus on work instead of fucking off on Hacker News or Facebook.

Now, as a self-employed individual I rent a seat in a shared open office to maintain that focus. It's far too easy to turn on the TV or play a video game or linger on the phone with a friend when I'm working from home. In a different setting -- with people around: all focused on work -- it's much easier to maintain a focus on work and getting done what's important.