They'll just think "oh god, I have viruses!" and call whoever is the family's "computer whiz". The very concept of "this system is not secure" is something that ordinary user does not understand.

Source: I'm a family "computer whiz" :/.

Many people still think that "Macs don't get viruses". Having that faith shattered can drive more than one away from the product.

That's true.

That's completely untrue, and pretty cynical.

People understand if a system is insecure, and now apparently all non-Yosemite Macs are insecure. Folks will grok that. Whether or not they find out about it, well that's up to you and I, and everyone else on this website.

I didn't mean it in a cynical way. From my observation, "it has viruses" is the best model that is self-consistent and yet doesn't require investing a lot of time in comprehending the workings of a computer. Non-tech people reach it naturally.

I agree it's up to us to proactively tell our parents, friends and colleagues who may be vulnerable about this problem.

I have to go with the idea that MOST people have no idea about security with their computers. Also most Apple people still say no bugs, no crashes and no viruses. Even when I point out every time something crashes on their Mac.