In IT, more than in other areas, the speed of technology development means that if you don't keep your skills up to date, your competence can fade away faster than in almost any profession that doesn't involve sports.
But, if his or her skills were up to date – and an awful lot of the 55-and-older geeks I know make sure theirs are, for exactly these reasons – why would someone in that age group be less employable than someone 20 years younger?
Is it an overall youth bias? Is it the salary issue?
Is it a perception that an older geek won't want to be managed by a younger one?
Is it intimidation on the part of the younger ones, who don't want to manage someone who's seen 100 whelps just like them come and go over the years?
You tell me. I don't get it.