I now have an unlisted number for the very same reason as stonhenge posted.
A client had called the office line and left a message. She then called my home number, at 11:30 at night. I didn't answer it, was too sound asleep. I saw the time stamp on the message when I got up, and listened to the message. "Give me a call AS SOON AS YOU CAN". So, I did. It was about 4:30 a.m. I called, obviously waking this person up. I apologized (HAHA) for calling so early, but explained to her my reasons; since she called so late at night, and left a message asking for a return call ASAP, I thought that there must have been some type of emergency.