Earlier quoted context omitted.
I signed up earlier this year and the validation required answering several multiple choice questions with data from my credit report such as mortgage, car loan, etc. I also received a postcard confirming that Informed Delivery had been activated for my postal address.
I see, so they do some kind of verification. Thanks for your reply! I guess asking about credit report info is inadequate if people are managing to abuse this. One problem with that kind of thing is it's essentially security by obscurity, it's not deliberately created secret knowledge that can be trusted, it's stuff which happens to not be public and which only you should know, but there's no guarantee and you can't…
I definitely received the postcard though.