I think that this article, though terse and generalistic, addresses a valid issue. However, I agree with many posters here in saying that it's not exclusively age that hampers older engineers, but an ossified skillset. Anyone who becomes entrenched in a nichey vocation then strikes out at 50+ to find new employment is going to suffer. The tech world worships youth and forgives hubris and foolishness, so it's especially unfertile ground.
That being said, as a serial startup founder, on a few occasions I've had developers working for me in their late fifties and even sixties. I was, in fact, in my mid to late twenties at the time, and I had great relationships with these guys. They had kept their skills up and their experience enabled them to sometimes do the work of ten people.
In my first company, I had a sixteen year old whiz kid who was possibly the most gifted hacker I've ever worked with, and we later hired a portly, bearded, late-fifties nudist Unix guy who balanced the youngster out quite nicely.
I'm now working in a startup where of the eleven of us, nine of us are in our forties, including three 40-something engineers. I've never worked with a better crew. And our stack is about as cutting-edge as would be responsible in a serious startup. Our VP of engineering literally helped invent Java at Sun, but moved on to new things later on instead of getting stuck.