Exactly. Why not just gather data gradually, and notice patterns in their behavior that seem to fit more with one temperament than the others. And maybe ask them a few questions about their motives?
Nothing wrong with doing that, but there are cases when if you are able to make quick, accurate type IDs it is useful to your purpose. For instance:
(1) Being a software sales rep. years ago (before I knew about MBTI) I would try to find out any little piece of info about the potential client that I could before meeting them. I went to a church that asked for a bid for some computers and basic network services. It was a last minute deal, so I grabbed an old gold cross earring from my teenager days and used it as a tie pin. The reverend was an ex-wrestler when he was in school. He said
"Son, I like your tie pin! You sure are a big fella'. Did you ever wrestle in high school?" Yup, I sure did for one year. We had a great chat, he was a really cool dude, and I got the sale. Knowing MBTI can allow you to make similar identifications with people that will allow you to kick off your relationship in the right direction.
(2) I've been a software/business process analyst for over 10 years. I get dropped into meetings of 10 or more people, all confused as to what they need to fix their organization's business problem, all stressed out over the deadline. Relax! First thing I do, find out who's the decision maker, who's the expert, who's shy and who's not. Guide these people into the solution by formulating it on a whiteboard, and getting them to talk about it with each other. Suddenly the idea is theirs, not yours, and they want to move forward with it. BOOM! Type ID to the rescue again. At this point I would want to be able to quickly pick out the Ns, Js, for sure. Es and Ps are easy to pick out, they identify themselves, I's also. My wife is INFJ, I can pick out NFs pretty easily at this point.
