The article is by Colby Cosh, and it is called Tarnished Silver: assessing the new king of stats.
It is an interpretation of Nate's PECOTA method from baseball, and the flaws it had - one major case in particular. I did not find the article to be convincing in an anti-Silver sense, but more illuminating regarding his past and methods. It seems that the major argument is that Silver is lucky. Repeatedly. At some point, I would argue, one has to concede that it's not luck anymore.
Cosh says:
The situation is that many of Nate Silver’s attackers don’t really know what the hell they are talking about. Unfortunately, this gives them something in common with many of Nate Silver’s defenders, who greet any objection to his standing or methods with cries of “Are you against SCIENCE? Are you against MAAATH?” If science and math are things you do appreciate and favour, I would ask you to resist the temptation to embody them in some particular person. Silver has had more than enough embarrassing faceplants in his life as an analyst that this should be obvious.
But, then, the defence proffered by the Silverbacks is generally a bit circular: if you challenge Silver’s method they shout about his record, and if you challenge his record they fall back on “Science is always provisional! It proceeds by guesswork and trial-and-error!” The result is that it doesn’t matter how far or how often wrong Silver has actually been—or whether he adds any meaningful information to the public stockpile when he does get things right. He can’t possibly lose any argument, because his heart appears to be in the right place and he talks a good game.