I feel like if you have to teach them about load balancers as college interns, FB needs to find a better school to pull interns from.
Also, don't mistake her teaching approach as indicating the people in the room weren't aware of what load balancers are or how they work. It's a good teaching technique to start out with some basic ground-work leading in to the point you wish to make. Starting out as she does ensures that everyone in the group knows _exactly_ what she's talking about before she gets to the key point, _and_ should be able to immediately understand what is going on and why.
Regardless of that, there's a lot of subtleties of dealing with load balancers that people rarely think of until they've been bitten by them. I've used load balancers quite regularly when interviewing candidates because I can almost always find some aspect of land balancers and load balancer behaviour that people aren't aware of. That gives me an ideal chance to explore a subject with a candidate and find out how quickly they can piece things together and learn.
The point of a technology degree had better be to teach you how to learn about new technology and experiment with it, or else a 2014 degree will be worthless in 2034.
No one hires MIT grads because they graduate with more extensive load balancer knowledge.
What it did teach me: locks, semaphores, mutual exclusion, the memory hierarchy, threading... the core concepts of concurrent and distributed systems that are independent of the specifics of running a large-scale web application.
Some degrees in CS are really vocational certificates, while more traditional degrees are not.