I had a similar conversation with Kraig a while ago, ‘cept we discussed whether companies should have booths or those sound blocking dome things for employees to make calls instead of in their cubical.
When people use cell phones in the office, it can be a disruption, especially if their connection isn’t so good.
Kraig’s point, which I agree with, was that people are less apt to stay on the phone too long if they can’t do so privately. Talk goes down, productivity goes up. I still like the idea, because people will have personal calls at work, privacy or not. I know it’s a tangent, but your post reminded me of it.