Not very related, but this is an example of a service (maybe just for me) I've wanted to setup with LinkedIn: Given company X, find all people that work or used to work there, then get rotation statistics. You should be able to see how many people (and %) go in and in what time on average.
I know of a smallish startup (70 people) where execs (VP and C level) rotated pretty often because of the policies of the CEO (was extremely cheap). It would be a great tool to have when exploring new companies.