Called at 1:00pm. Diverted by a service I subscribe to that intercepts robo-dialed calls (rhymes with SoNoHobo). I called back (*67) and got, "The number you dialed is not in service. Please check the number and try again. Good bye." (Spoofed number)
Think about it. How *else* can you learn that it is not in service, thus learn that the caller spoofed (faked) the number? And if I called withOUT using the shield of *67, they would know that my number is "live." The whole idea is to learn what I can about them without them being encouraged to keep calling me.