The problem with all these debates about "optimal" office layouts is that they're all a series of non-repeatable experiments: someone can always say "Sure, you were successful doing X, but if you'd done Y instead you would have been more successful."
The hypothesis that Y is superior then becomes non-falsifiable: if someone doing Y fails, it wasn't because they did Y it must have been another factor, and if someone not doing Y succeeds, then they would have been better off doing Y. At some point, the argument becomes completely unhinged from any real-world experience.
So really, all I can say is: we have open-plan offices, and we've been successful/productive/kept employees happy, so clearly it is possible for open-plan offices to work. For someone that's convinced that open-plan offices can't possibly be a good idea, and who rejects other people's real-world experiences, what is there left to argue over? The hypothesis becomes non-falsifiable and there's no point talking about it.
To your point about conversations, when people are sick or on leave or working remotely those conversations don't happen and we suffer as a result. We haven't found any replacement for impromptu conversation, or for gaining knowledge through overhead conversations, and so on.
Just as a stupid example (though this sort of thing happens all the time), suppose Chris goes to ask Bob a question, and Alice is setting next to Bob. Bob thinks the answer is that you have to do A, but Bob's wrong, and Alice knows it: the right answer is now to do B. On top of that, Denise, who's also sitting there, hears the answer as well, and just learned something effectively by osmosis.
If Alice wasn't sitting there, able to hear the question, she wouldn't have jumped in, and Chris would have gotten the wrong answer and wasted hours or days doing the wrong thing. Denise also wouldn't be clued in to how things should work either. If Bob had a private office that Chris went to, or it was a one-off IM or phone call, you'd have the same problems. Did everyone get a little distracted by overhearing that conversation? Yes. But ultimately, that productivity hit was worth it, because Chris was saved a ton of time and Denise and Bob gained useful knowledge.
If you can convince people to use something like Campfire where they route all communication through such that people who are remote or momentarily absent are included, I think that can take the place of overhearing those conversations, but it's impossible (in my experience) to convince people to do that when they're working in the same building: people would rather just go chat face-to-face since it's much higher bandwidth than typing.
You're right, office conditions are notoriously hard to research because variables are abundant. However, there are ways to measure it empirically. In the design of an experiment like that, you'd want to use metrics that are heavily dependent on the change. Measuring financial outcomes is no good, because they are affected in significant ways by a number of other factors (including a large factor of luck).
A better metric for this kind of research could be stress levels because they are significantly dependent on changes in physical working environments. Stress is affected by a number of other work factors, such as management, work/life balance and workload, but these can be measured and controlled for. The effects of stress on various performance outcomes are fairly well understood, so this relationship can be used in tandem with other variables to ensure that a change is having the hypothesized effect. Again, it's not simple, but it's far removed from having no comparison.
I wouldn't suggest using online communications for every decision, but rather recording the essence of each substantial conversation digitally. Tasking one person with sending an e-mail containing the conclusion of a discussion takes a fraction of the man-hours consumed by a conversation, especially if many people are frequently involved (which I still advocate against).
Further, summarizing by e-mail is an aid to people's memories, helps avoid miscommunication by establishing a mutual understanding, and chronicles decisions and progress for later review or lookup.
Just FYI, I think that really depends on what kind of a person you are.. Some people prefer to write because it gives them an opportunity to explain things in an ordered, and well thought out fashion.
That is a great example and happens all the time. This can be handled decently well by something like Skype, or just using code reviews and design reviews like professional engineers we claim to be.
The hypothesis that Y is superior then becomes non-falsifiable: if someone doing Y fails, it wasn't because they did Y it must have been another factor, and if someone not doing Y succeeds, then they would have been better off doing Y. At some point, the argument becomes completely unhinged from any real-world experience.
So really, all I can say is: we have open-plan offices, and we've been successful/productive/kept employees happy, so clearly it is possible for open-plan offices to work. For someone that's convinced that open-plan offices can't possibly be a good idea, and who rejects other people's real-world experiences, what is there left to argue over? The hypothesis becomes non-falsifiable and there's no point talking about it.
To your point about conversations, when people are sick or on leave or working remotely those conversations don't happen and we suffer as a result. We haven't found any replacement for impromptu conversation, or for gaining knowledge through overhead conversations, and so on.
Just as a stupid example (though this sort of thing happens all the time), suppose Chris goes to ask Bob a question, and Alice is setting next to Bob. Bob thinks the answer is that you have to do A, but Bob's wrong, and Alice knows it: the right answer is now to do B. On top of that, Denise, who's also sitting there, hears the answer as well, and just learned something effectively by osmosis.
If Alice wasn't sitting there, able to hear the question, she wouldn't have jumped in, and Chris would have gotten the wrong answer and wasted hours or days doing the wrong thing. Denise also wouldn't be clued in to how things should work either. If Bob had a private office that Chris went to, or it was a one-off IM or phone call, you'd have the same problems. Did everyone get a little distracted by overhearing that conversation? Yes. But ultimately, that productivity hit was worth it, because Chris was saved a ton of time and Denise and Bob gained useful knowledge.
If you can convince people to use something like Campfire where they route all communication through such that people who are remote or momentarily absent are included, I think that can take the place of overhearing those conversations, but it's impossible (in my experience) to convince people to do that when they're working in the same building: people would rather just go chat face-to-face since it's much higher bandwidth than typing.