I switched my elderly mother to Ubuntu a few years back and she recieved one of these calls. Acording to her it went something like this.
Caller: This is *** from *** we noticed that there is somthing wrong with your computer and we are calling to help you fix it.
Her: Okay, let me get on my computer. What's wrong with it?
Caller: We have recieved notification from your computer that it has spyware on it. It has notified us and we are calling to help.
Her: Okay, I'm in front of my computer. What do I do?
Caller: First, click on the start button.
Her: I don't have a start button.
Caller: It's the icon on the lower left that says start.
Her: I don't have one of those. I have Yoobunto, Ewebantoo, I don't know, my son put it on here...
Caller: Please just click the button that says "Start".
Her: But I don't have one of those.
This apparently went on for several minutes. Finally she hung up and called me. If she was running Windows, she probably would have gone along with the scam. This is not to say that the problem is with Windows, but rather that, as long as MOST people use Windows, there will always be an idiot to be found and these scams will occur.
But imagine the problems these callers would have if Debian, (or Debian based), systems were the norm...
Caller: Okay, which desktop do you have installed?
Her: Desktop? What do you mean?
Caller: What does your screen look like?
Her: Flowers. I found I nice picture of lilacs.
Caller: Umm... Can you open a terminal?
Her: What's a terminal?
I don't think these scammers would even gotten started.