Sorry, Aaron, my post wasn't actually in response to your comment, although the proximity suggested that. I don't disagree with anything you've said in this thread. [Unless I misunderstood what you meant by "no" to Mark's question. Which is quite possible.]
James, I think part of the problem of disappearing common ground is that disagreements among friends and colleagues tend to be very public now.
This respectful argument between Auden and Cerf might not have been as conducive to mutual understanding if the whole thing had taken place in a public forum. (And yes, I am aware of the ironies of my referring in a public forum to a private disagreement that has now been made public.)
It's far easier to come to a consensus between two people than among dozens or hundreds, many of whom feel deeply invested in what they perceive as their own side winning the argument and the other side losing.