Age discrimination worried me a lot when I was in my 20s, and I really don't get the feeling that most young people have some delusion that they'll never get old. Whatever is going on, I really don't think it's based on a general prejudice from 20 somethings toward anyone over 40. I don't have a cite, so this is just a hunch, but my guess is that age discrimination is more driven by execs who are the same age as the more experienced programmers, not from the younger programmers.