The relative ease with which called-IDs can be spoofed seems to be one of the major "tools" with which scammers can gain the trust of their victims (or trick other systems into believing that they are the victim). Most of the non-technical folks I know will also more or less blindly trust a caller-ID. Fortunately, many scammers (at least here in Europe) are still calling you claiming they are interpol following up on your Paypal account being breached whilst a +233... number shows on your phone.