Pointing out that Facebook likes don't increasing rankings doesn't debunk Google +1s. Obviously you know if they do or do not affect rankings. I'm not sure you would tell us if they actually were used as a signal in rankings because that would lead SEO's to focus on +1's in a way similar to what happened with pagerank. It could also lead to +1 spamming/exploiting.
Not that I'm going to believe you anyway, but I just want to clear this up. Are you, Matt Cutts, saying that +1s make no difference in Google rankings?
Agreed - perhaps he could have used more explicit language but, as you rightly said, I think he had answered that question already. I know he's public enemy #1 amongst some SEOs but people should stop being so rude to the guy!
I don't know if your comment is directed at me, but I don't feel I was rude to him at all. I do see a lot of hate for Cutts from SEOs, but they hate Google anyway. Cutts is just a face to Google that they can focus on.
But that is not saying the same thing. Your interpretation of it is "Yes. I am saying that +1s make no difference in Google rankings." but that is not what cutts said. His answer leaves it up to your interpretation. He could be saying "people who say +1s have an effect have no way of knowing that for sure" because we don't have access to their algorithms.
I may be misunderstanding the basics, but the article implies that putting a post onto plus gives you a "perfect" page for SEO. Which means that any links to it will raise it's score more than any other page hosted anywhere else.
(They fail to follow through with posts on G+ are naturally likely to get more +1s than likes, thus presumably debunking the whole correlation issue like you say. But anyway)
So my takeaway (which I am not sure if you are challenging) is that posts on plus.google did better than a presumably control sample on facebook - and the article incorrectly ascribes this to +1s. You seem to be saying, yes it did do better but its not because of +1s, its just better. But is it better content or is it better SEO-ness of the page.
Thats the part I would like to see these studies show - how they manage the control portion. How they control for quality of the content? Because if posting the same content on G+ and on a.n.other site gets you significantly more pagerank, then its really hard to argue not to do that.
(I quite accept the "its not +1's goddammit" argument)