I posted about professors and the policy world over at Duck of Minerva, and one of the responses repeated an oft-told myth that having policy experience is bad for one's career. I have no stats to back me up, but my impression is that having some policy experience is not harmful to one's academic progress.
In the post, I mention a bunch of scholars who dipped their toes into the policy pool and yet managed thrive afterwards. In my experience, having the one year in the Pentagon has been obviously and measurably good for my career. My competitor for the McGill job way back was also a CFR International Affairs Fellow--that it seems that having policy experience was seen as a qualification for the job. I am pretty sure that my year in the US government also helped me get my current job since it is at a policy school. The experience also opened up a series of questions that led to a major research project that has occupied much of the past several years, one for which I have received several grants and have published in prestigious places. While the pubs are not super-policy oriented and I am still trying to get something published in a more policy-oriented outlet, my career has certainly thrived despite, nay, because of the taint of the policy world.
It may be the case that it is hard for someone who has worked in the policy world a decade or two to make the transition to the academic world, as pubs do matter. And if you publish all your work in policy oriented outlets, that may hurt one's tenure case. But in general, I find it hard to believe that crossing into the other world for periods of time is damaging to one's career.
Or am I wrong about that? Are there cautionary tales of which I am unaware?