It was certainly attempting to capture something useful about the test-taker's approach to interaction and problem-solving, though -- unlike astrological signs

It was certainly attempting to capture something useful about the test-taker's approach to interaction and problem-solving, though -- unlike astrological signs and similar things (which are based only on birthday). Of course, it depends on the context -- I'd be distressed to run into this as part of a job interview -- but in general the people taking it seriously are trying to figure out ways to help people with different styles of thinking/working interact with each other. On the whole, this is worth some effort, and you should encourage it (while gently dissuading them from using the MBTI as the starting point...).