They're good for physicists, if not over done. In an interview situation, I'd regard them more like a parlor trick - it shows someone has been taught how to do estimates like that, but little else.

One I heard in college was - "Give me your estimate of how much this building weighs." I don't recall the answer, nor being taught how to figure it out other than ("Well, you know how much a brick weighs, so ...").

http://www.physics.u...g/fermi/fermi.htm

Sometimes you need a reasonably quick and reasonably accurate way of figuring out orders of magnitude, etc. It's a skill that can be handy but is probably rarely taught. I agree it is no substitute for understanding how well someone works with others on a project, or how they think, or how they approach a problem, or whether they want a checkmark on a resume or whether they want to grow with a company, or ...

Cheers,
Scott.