Let’s assume that every minute of talk time costs the phone company some amount of money to provide. In this scenario, they would have a financial incentive to block abusive callers, like the automated messages that peddle car warranties and mortgage refinancing. With access to the call data for millions of customers, surely they could spot the patterns that characterize the spam calls.

However, I’ve never heard of landline or cell phone companies trying to block abusive callers on a systematic basis. This leads me to an interesting theory: Either the phone companies enjoy the extra airtime charges that customers incur from the bogus calls, or the cost of providing those extra minutes of talktime is actually zero after all.