[ajuc]

What adventages this question has over asking candidate to write factorial, or FizzBuzz, or sth like that?

It only checks if you can estimate the thickness of paper sheet and know powers of 2. Anybody can know that.

[wlievens]

Perhaps if you show that you need (a) the thickness of paper and (b) the powers of too, you've shown the thinking ability to pass the question. The result value doesn't matter.