I just came across a very alarming article about olive oil in the Hartford Courant: Impure olive oil? Say it ain't soy. If you have a friends or family with a soy allergy, please read this article.
Apparently some imported "olive oil" isn't olive oil at all; it's soybean oil and it's being sold much cheaper than other, real olive oils. Not surprising, the "olive oil" does not bear the required allergen statement indicating that it contains soy--that's frightening. It seems reading your labels is not enough; if you see something that seems exceptionally cheaper at the supermarket, you may be well advised to make calls, send emails, and ask questions regardless of what the label says.
The problems with impure olive oil have spurred the olive oil industry in the U.S. to work on setting standards for olive oil purity, with Connecticut leading the way.