In the US, the best example is in California. To get the California Olive Oil Council stamp of extra virgin quality, you must have your oil tasted by the government body. I'm one of such tasters :)
This is why I mostly buy Californian olive oil now. I like the legit italian or spanish kind more, but it's faked so often in the grocery store that it isn't even worth attempting to decide if it's real. Sometimes the fakes tell you it's cut with olives from africa, and sometimes they don't. The US importers are held to no standards whatsoever. At least when I buy california olive oil, it's 95% of the way there and guaranteed to be real.