First, some right-winger decides to steal the idea for Freakonomics for his own book, down to the cover and everything.
Then, Noam Scheiber decides he's sick of it and takes the idea of natural experiments in economics to task for ruining the discipline.
Poor Steven Levitt. Alas, it's just a nerdy backlash a la dismissive indie rockers: "If it's popular it must not be good." And vice versa.
I still think Freakonomics is a really good book, and unlike some critics, I don't think it just gives us small answers to small questions. Nor do I think it comes to the same economic conclusion everytime: that people will always act in ways that serve their own best interest.
For me, these natural experiments serve a sociological role of helping us to identify competing interests in even the smallest of every day interactions. It seems to me if you add all these up you'll come to larger conclusions about larger forces in the world.