Yesterday I got an interesting offer from Verizon in the mail. They have this new feature called 'Call Intercept'.
Call Intercept stops calls that do not provide a valid telephone number. These calls appear as "anonymous," "private," "out of area" or "unavailable" on your Caller ID unit. Call Intercept will ask unidentified callers to record their name before your phone rings. When you pick up, you'll hear the recording. So you can decide whether or not to take the call. If callers refuse to give their names, their calls won't get through. That way your phone doesn't ring and you won't be bothered.
It's definitely an interesting idea. But I don't know that I'd pay $5/month for it. But if I was getting a lot of annoying calls I might think about it. If I was still using my land line.