On the one hand I agree with you: no one should be expected to justify their life. (Who would have the wisdom to judge, anyway?) But on the other hand, I do think it's useful to ask whether the limited supply of genius in our society is being well-employed. Thinkers in the finance industry worry about this a lot, for example. Is it really a "good thing" that huge pools of quantitative talent are being drawn away from math and physics towards complex derivatives trading? Is shaving a few fractions of a fraction of a fraction of a second off the duration of a securities trade a good use of their time and talents? While I agree the original comment could have been more sensitive to the real person on the other side of the screen, I still think it asked a useful question and we're getting a good discussion out of it.