1. A method performed by a call answering system for identifying unwanted callers, the method comprising:forwarding calls that are unanswered by a plurality of telephony devices to a call answering server;
identifying, by a call records server, phone numbers of the unanswered calls;
collecting, by the call records server, information from the plurality of telephony devices that is related to the phone numbers, the information including whether the phone numbers are pre-existing contacts of a majority of the plurality of telephony devices;
determining calling patterns associated with the phone numbers based on the collected information;
calculating a probability for each of the phone numbers as being unwanted based on the calling patterns; and
categorizing given ones of the phone numbers as unwanted callers based on the calculated probability.