But even then, you'd be surprised how many people don't even do that.....

Even so, I usually ask something that is barely more difficult, like traverse a tree, or reverse a sentence.

There is no point at all in asking the hardcore, Google interview questions, as a simple question tells you just as much, which is "do you have a pulse".

I got asked compiler question once. How to find dominators. I haven't had to find dominators for a very long time other than from a college course, mostly only used them. Looking it up, it's definitely not something you can come up with because it's so clever.

Those questions tell you more about the interviewer than the interviewee.

Was this interview for a compiler position?

Anyway, dominators make sense for arbitrary directed graphs (with a notion of root).

yea, but for a target dependent backend position.

If a candidate can google the problem, understand it, and then learn how to write a simple variation of it they have demonstrated all the skills necessary to be a useful coder at an awful lot of companies. I'd kinda prefer them to learn basic programming a little more ahead of time, but I honestly don't care when you learn how to program.