Poking around on Cosma Shalizi's website, I found this long, somewhat technical argument for why the general intelligence factor, g, doesn't exist.

The main thrust is that g is an artifact of hierarchal factor analysis, and that whenever you have groups of variables that have positive correlations between them, a general factor will always appear that explains a fair amount of the variance, whether it a actually exists or not.

I'm not convinced, mainly because it strikes me as unlikely that an error of this type would persist for so long, and that even his conception of intelligence as a large number of separate abilities would need some sort of high level selection and sequencing function. But neither of those are particularly compelling reasons for disagreement - can anyone more familiar with the psychological/statistical territory shed some light?