There's no question that face to face conversations can sometimes be quite "productive" in terms of efficiency and being able to pick up on non-verbal cues. At the same time, forcing people to come into an office with the expectation they'll suddenly become social and fluid in non-FTF communications is just plain ignorant. And for every potential benefit that colocation/FTF convos enable, there are also a downsides such as distractions from loud talkers, smells, etc.
Being socially aware, open and willing to share thoughts and ideas can't just be dictated onto someone. I've come to think that many people – especially software developers – must be encouraged and cajoled to open up. It seems many are afraid or intimidated of the thought of having to actually "document" themselves. But having some record of ideas and who's contributing what can be challenging in a "voice-only" environment. I suppose it's human nature to be reluctant to go "on record" as is generally required of IM, video conferencing, wikis, etc.