At my first job, 6 of us (all programmers) sat around a large conference table. If I had a question about the code, I peaked over my laptop's screen, someone else noticed and asked "What's up?" It was great for that quick collaboration, but it also exposed us to every annoyance possible. There was a guy who burped a lot and liked to sing show tunes. The guy next to me bought me earbud-style headphones because the cheap ones I was using leaked out a lot of sound. We also needed an always-be-working atmosphere to prevent a conversation unrelated to work from taking more than 5 minutes.

I've had my own office for the last 3 years and enjoy the privacy, but occasionally miss the instant answers and social aspects of that open plan.