Gladwell is a writer. If you write enough, eventually you're either going to make factual errors or state opinions that people disagree with. In this case, being "wrong" simply means she disagrees with his opinion.
I generally enjoy Gladwell's writing in the New Yorker (haven't read any of his books) and enjoy hearing him on Radiolab, but there has been at least one case before where he has made oversimplifications. When noticed, they pretty much upended his thesis.
His article "How David beats Goliath" asserted that smaller, weaker competitors beat their stronger, better equipped opponents by dramatically changing or breaking the rules of engagement.
One of the examples was average or weak high school basketball teams using a full court press technique to defeat the best teams in the league. The other example is Lawrence of Arabia defeating the Ottomans at Aqaba. In letters which were published later that summer, readers pointed out that a full court press is used by many "Goliath" teams, and that the Ottomans were actually the underdogs since Lawrence of Arabia had the support of the British Empire.
I'm not a basketball person or a historian, so maybe the letters were off, but the New Yorker did publish them, and they certainly did make me question the article which I had so enjoyed a month before.
"He provides misleading definitions of “homology,” “sagittal plane” and “power law” and quotes an expert speaking about an “igon value” (that’s eigenvalue, a basic concept in linear algebra). In the spirit of Gladwell, who likes to give portentous names to his aperçus, I will call this the Igon Value Problem: when a writer’s education on a topic consists in interviewing an expert, he is apt to offer generalizations that are banal, obtuse or flat wrong. "
Well, everything. In short, his system of coming up with a folksy sounding counter-intuitive theory, followed by a couple of interesting anecdotes and a tame scientist which "prove" his thesis, does not tend to consistently lead to truth. Or in fact lead to truth at all.
In the cases where he is correct (if only by dumb luck,) it's still not helpful since you don't know which ones they are without doing the legwork yourself.
It is intellectual slop, ideally suited to the best-seller list of a major sunday newspaper, but it is not true or even some approximation of it. If that's how you like your social science, then have a bowl of Gladwell.
I assume the 'Again' is a reference to the fact the author wrote another piece disagreeing with Gladwell about something else - see the first paragraph of the article.
