When we received him in our interview, we asked him to tell us a bit about his past projects, what he liked, disliked, etc. He didn't talk much and it took us a lot of questions to dig up helpful things.
Then we asked a couple programming related questions and he bombed them all. He couldn't put an algorithm into words, write code that compiles or gives the proper results. Our interview programming questions start very easy and we slowly iterate by adding more constraints that shows if a dev has a deep knowledge of the language and framework.
I have a feeling like this developer was good when he's working alone on a project with no one to talk to. He would have never fit in our company culture and we couldn't evaluate his skills in an interview.
or he/she could have faked the resume, or dressed it in a good way. I find that excellent programmers tend to be good communicators, because good, clean programming is about communicating with future programmers (which could be yourself in 5 yrs time). Having clarity in thought and being able to express ideas to other people is so crucial that i would rank that above experience with a certain stack/tech.
However, rather than re-hash all that, it's worth taking a look at the numbers - numbers that absolutely indicate a younger skewing workforce. For instance, the average age at Facebook is 26, and 31 at Google. Tech as a whole leans young, with the "oldest" tech company workforce (HP) still younger than the national median [1]
Now, whether simply having a younger workforce points towards actual age discrimination is a matter of fair debate. A perfectly reasonable explanation might be that tech is a young field, hence a young workforce. However, there are enough confounding factors (limitations of experience, work/life balance in dev roles, etc.) that certainly make for rational arguments in favor of age being more of burden than boon.
Then, of course, you have stuff like this :
> "Young people are just smarter. Why are most chess masters under 30? I don't know. Young people just have simpler lives. We may not own a car. We may not have family. Simplicity in life allows you to focus on what's important." -- Zuckerberg
True or not, it would be weird to argue that his opinion is somehow a rare isolated outlier. It speaks to a common conception - both in the valley and in tech - that this is a business for the young.
[1] http://bits.blogs.nytimes.com/2013/07/05/technology-workers-...
Most programming work doesn't require a genius level iq. It requires being able to build simple things very, very quickly. As a result, the experience level at a company matches the structure pyramid. The smart, older guys at the top make all the tough decisions and the fresh, younger guys at the bottom code as fast as they can. As those at the bottom age, they find themselves competing with other programmers their age for far fewer jobs toward the top of the pyramid.
In others, especially those with the high-strung startup mentality you mention, they are looking for people to work more hours for less pay and promises. Younger people are more able / willing to take risks. Experienced workers are not as interested in promises, but prefer defined returns on their individual investments.
Since he was explicitly told that they wouldn't be sending his resume to anyone else that pretty much means the failings are purely resume-based, not ability or interview skills. I have a hard time picturing a resume making one unemployable other than due to age discrimination.