The introduction of voice mail at work is what killed the efficiency of telephone communication. It became very easy to let a call go to voice mail, and then claim you never got the message, or your voice mail wasn't working, etc. It was much harder when when a secretary took your calls and kept a log of messages.

Voice mail and then email (esp. auto-responding "I'm out of the office") became great work-avoidance enablers, whereas before the telephone was a great productivity enhancer.