Even though CS fundamentals and contributing in teams are somewhat different skills, in my experience the terrible developers that contribute negatively to the project tend to be those that do not have a good grasp of CS fundamentals.

I mean, some problems we are faced with are very, very challenging and if somebody can't figure out how to reverse a binary tree or do a FizzBuzz, then what can he do?

Also I'm hearing this advice to hire engineers recommended by other engineers quite often, however speaking as somebody constantly engaged in hiring decisions at our company, I must say that recommendations don't scale.

You see, outside the SF bubble of course, our friends are mostly not into software development and we engineers are kind of introverts, goes with the territory, so we don't have that many friends or acquaintances anyway, except for people that we meet on the Internet, which usually live in another city or country. If an employee can produce one good recommendation, that's way, way above the average. It's such a rare event actually that such employees need reward.

This advice also misses the point. The problem is that our industry is constantly growing and there aren't enough good people to go around. Which means we have to take the plunge and hire beginners as well. Investing in the education of beginners is the only way a company can scale in talent. But even then you need a filter. You can't hire anybody that walks through that door, as firing people is a serious drag on morale and a net loss for the company.

So what filter can you apply to beginners? CS education of course, or in other words what people should have learned in school.