How Many Get Bumped Up to the Majors?

Over at Drug Monkey, PhysioProf writes that there are two functions to being a postdoc. One is training and the other, he writes, is selection. He likens postdoctoral training to minor league baseball: "It is necessary training to learn how to play ball in the major leagues, but it is also a selection mechanism to identify those players who have a decent shot at success in the majors." PhysioProf goes on to say that that long postdocs should be embraced by those who want to be PIs. Two years, he says, isn't that long to show all that you can do and that five or more years is certainly enough to show all that you are capable of doing. YoungFemaleScientist takes some issue with the post's points, calling them, among other things, "offensive and stupid."