I would suggest those who are interested in the literal psychology of employee retention do some reading of the academic research on the subject.

There's an interesting review of the literature about job burnout, for example, that was published in the Annual Review of Psychology in 2001.

http://igitur-archive.library.uu.nl/fss/2006-1104-200110/mas...

I know that psychology isn't held in as high regard around here as the harder sciences, but as much anecdote about the laws of human behavior as there is on HN and in the startup scene in general, I'd think there would be more interest in what science has to say.