Note, that I was and am raising a question, not making an argument.
Let's assume that open office floorplans result in a decrease in productivity. The author mentioned that the open office plan did create a sense of camaraderie. Suppose that people attrited or you lost out on recruiting talent because your office felt too old-school, or they left because other startups felt more fun. This is one instance where long-term productivity could suffer for the sake of near-term productivity.
I'm not saying that this happens, but it's something to consider. In fact, we're in the process of selecting office space right now, and it's a lot easier to find law firm style offices with only rooms - no open space. We've decided against it - and are going with open space (plus a few quiet rooms) for a couple reasons. First, we don't want to lose out on the fun factor. Being able to shoot the shit with your friends may be distracting, but it makes the workday a lot more bearable. Our particular dev team actually agrees with this, but I could definitely see the counter argument. The other reason is that it makes much more sense for our sales team, call support, and operations guys to be able to shout questions to each other in real time. Try giving an inside sales rep his or her own office - their numbers plummet because they are no longer immersed in the competitive environment of a sales floor.
Any way, I'm just trying to make the point that there are downsides to having a traditional cubicalized office that could erode the immediate benefits.
Sounds like an extreme position you're taking. Anecdote to disprove your negative - one day I was talking with a customer about an issue, one of my open-office coworkers heard me then IM'd me an internal forum page that helped me seamlessly resolve the issue.
Were I working from home or out of that persons earshot, I would have dug around for potentially hours or days before finding my solution.
Were I heads down writing code a lot (I don't do that very often these days), I'd head over to the private (no-noise-policy) work rooms nearby.
