There must thousands of people involved in this racket for it to be on the scale it apparently is .
There is almost an epidemic of this in going on in 'my' part of Australia. I get one of these about every three weeks.
Last night it was mentioned amongst a group of friends during coffee and almost everyone had been confronted with one of these calls in the past few weeks.
A few days ago we were at relative's place (normally vacant) doing some spring cleaning, and there were three such calls in the five hours we were there.
The tragedy is that some people must actually believe them and go along with the scam. Otherwise it should have died off by now.