[santaclaus]

I know a non-negligible number of new professors who, when offered faculty positions, negotiated a later starting date to pursue a postdoc for a year. Postdocs are a great low risk way to expose yourself to different research groups, to undertake crazy projects that you might not be able to do at your next institution, and to expose yourself to new communities (eg a theory CS PhD working in a math group) and to other researchers. Postdocs are also, in some sense, the most freedom you'll have as a researcher. As a grad student you are more beholden to an advisor than as a postdoc, while as a professor you have administrative duties, recruiting, teaching, and all that jazz distracting you from your work.