When interviewing I would often ask one (and only one) question of this type. The rest of the interview was your standard set of questions to see what type of p

When interviewing I would often ask one (and only one) question of this type. The rest of the interview was your standard set of questions to see what type of person you were sitting across from. The one "brainteaser" question was "Estimate how fast human hair grows in miles per hour. Order of magnitude is fine." I just wanted to see that they not only knew how to estimate something but that they understood this particular estimation wasn't important given the job they were interviewing for and could thus be answered quickly rather than accurately. The one person who answered immediately was off by 3 orders of magnitude but he was the best hire we had. He could spot BS a mile away.