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.

For other people's takes on him, try:

http://news.ycombinator.com/item?id=1063576

http://philip.greenspun.com/flying/foreign-airline-safety

http://blog.jgc.org/2010/06/how-to-write-malcolm-gladwell.ht...

http://www.fastcompany.com/magazine/122/is-the-tipping-point...

http://www.vanityfair.com/culture/features/2009/12/gladwell-...