I have a small theory about this trend with IT that you observe:
Firstly, because the job is more mental (than physical, I mean) you become that much more aware of your mortality (i.e., burn-out rate) than other jobs. Secondly, after the inital lure (and lucre) wears off, you find the job is quite repetitive, boring and does not involve "building new bridges" everyday as you had earlier thought, but painting old bridges and touching them up here and there. There's the odd flash of brilliance that makes your day, but otherwise it is just same ol... same ol...
So, you look around for alternatives.... The path of least resistance is the ready tools of our trade available for us that we use for info... THE NET. Sooner or later we will end up in one of the early retirement forums that are out there in cyberspace.
Correct me if I am wrong or missing something?