My rule of thumb for a ringing telephone is, "Is there anybody I want to talk to more than whatever I am doing right now?" and the answer is inevitably NO.

This has been an interesting benefit of going cell phone only. If I have it on me, it is in silent mode since I will feel the vibration. I can easily and quickly take it out of my pocket, look at the caller ID, and decide if I want to answer. If not, I hit a reject call button, and they leave me a message that I can listen to at my leisure. Or, if I know for certain I don't want any calls, I have the power button. Turn it back on later, and if it tells me I have new messages, I can listen to them then.