It actually makes sense. It's not about age. Middle management has an expiration date. If you've been a middle manager for 15 years, that's bad bad bad. (Being an IC for 15 years is respectable; but once you move into management, you should make director in 5 years and VP in no less than 10.)
Programming has an ageism problem largely because it's run by career managers (who think all of us want to be them-- and we don't); engineers themselves aren't ageist. Management is where the ageism comes from and it's even worse in their world. It's not that they care about age so much as they want to avoid hiring terminal middle managers, and I can't blame them for the latter. This fact has absolutely nothing to do with age, but terminal middle managers are toxic.
You can be fairly confident there some startups out there founding by 20 somethings, populated by 20 somethings, who think having someone over 30, or certainly over 40, on their team or even in their office would be akin to the plague. They would probably place them in the same camp as their parents.
I totally understand why coders like Agile, hey I like it because hacking code is the fun part :) Its also kind of a good fit for the app store era, where you throw something out there and see if its sticks before you actually develop most of it. Not entirely sure its actually a good way to develop nontrivial software.
It's not that people with 12+ years of experience are not as good. We were trying to screen out candidates (many of them who are smart) but have been "managers" for so long that they can't get their hands dirty and solve issues themselves (something you have to do at a very small team).
Don't take my word for it, 26% of people on our team are older than 38. If you're bored, check out their bios at 500friends.com/team
Admittedly however, this was not clear in our post, and it has since been edited.
If in your 20's you feel, some one over 30's is a plague. You have a big reason to be worried, because you will be in your 30's in less than 10 years. That's too less time for comfort.
Programming has an ageism problem largely because it's run by career managers (who think all of us want to be them-- and we don't); engineers themselves aren't ageist. Management is where the ageism comes from and it's even worse in their world. It's not that they care about age so much as they want to avoid hiring terminal middle managers, and I can't blame them for the latter. This fact has absolutely nothing to do with age, but terminal middle managers are toxic.