When I worked at an open office in Google, a good fraction of the people had headphones on most of the day. While there was some serendipitous discussion, much of the time we'd book meeting rooms, specifically to avoid distracting those around us.
Open plan offices are indeed terrible, but that doesn't contradict the benefit of face-to-face communication. For me the best environment has been a large team office with 4-8 people, where everyone has a decent amount of personal space and spontaneous discussions are more likely to be relevant.
