Hey Rita - have to say I've always been suspect of the oils on the shelves here in the US, as I really have no idea how to tell if I'm being taken advantage of other than taste. I have actually taken some back.
That said I'm really hesitant about paying top shelf for something I figure is old when I get it anyway.
So I go by a mix of flavor, color and price. As far as big chain - I've been buying one or two versions of Trader Joe's brands for quite few years as standard. By flavor more than anything else. I know it says EVOO on it but have always been distrustful of that as just a label.
While in Italy this year I did have the opportunity to have a good bit of what I'm sure was the real thing. By taste I would say what I have had in the US, some come close.
As informative as this article was in terms of a warning - it really doesn't tell you how to "tell" or judge as a consumer to protect yourself from over paying, etc or how to make sure you are getting the real thing.
Most Italians send their olives off to a processor who comes around during the harvest. At least that's what the locals told me while I was there. Those I visited had large stainless containers (looked like milk containers).
They gather their olives - the processor comes around and picks them up, then drops off their share after processing based on the amount of olives were provided.
Have no idea how the huge operators in Italy work.
Olive oils (and the olives) I had while visiting locals was exquisite. I missed harvest time though. Next time I visit I'd like to be there during the festivals. Regardless I think I learned how the real thing ought to taste at least.