Jonah Lehrer considers that age-old question.
I've never done blind tastings, but I'd like to try doing it sometime. All wines do not taste the same. I have had my share of borderline undrinkable, or undrinkable, wines, and my share of mind-blowingly delicious wines too.
It's hard to believe, but we've all read, and Lehrer confirms, that in blind tastings few can even distinguish a red from a white. I'd be a skeptic on that.
I think the meaningful question is whether the average wine drinker can tell the difference between a pretty good cabernet, for example, and a very fancy one, and whether the difference matters much.