I'm glad this discussion has come up... and is gaining steam. Personality theory is only hooey when you've learned about it from those who don't really understand it. Properly utilized, Myers-Briggs type-ology does nothing more than help someone recognize their own tendences, preferences and patterns of behavior (social, attentional, decisional, presentational). Properly applied, it helps us all understand how and why persons with various dispositions tend to process the same input differently.
The title of David Keirsey's bestselling book is called Please Understand Me for a reason. I believe the subtitle of my original copy said "Understanding how others misunderstand you". Now who wouldn't be helped by that? You can pay hundreds of dollars for professional psychologists to give you a full battery of personality tests, and there probably are some professionals who misuse myers-briggs theory as a way to pigeon hole individuals, but Kiersey's book will give you the true scoop AND explain the best possible motive for learning typology: It is NOT okay to go through life trying to make everyone else just like yourself.
In the four broad categories - NT, NF, SJ, SP - there are strong tendencies that help explain major aspects of people's lives, like careers. Most high school teachers are SJ's. Most college professors are NT's. I'll bet anyone money that more than 50% of bibliobloggers will come up as NT's. I tag every biblioblogger who reads this to learn their type (if they don't know it already) and post something about it. Typological testing subdivides each of the four major types into four others, but the truth is that's only the starting point. What causes someone to be social or antisocial? What do they apprehend quickly? What have they found to be reliable methods for making decisions? Which side of these processes do they more often display to the world?
By generalizing about ourselves, we begin to see connections between preference and disposition. By generalizing about others, we begin to see how futile it is to try changing someone else's core dispositions. (*** That doesn't mean you can't change someone's life for the better; it just means you might have to come at them differently in order to be effective about it. ***) In the course of maturing, people tend to balance a bit across all major categories. In the course of studying personality types, people tend to learn that nobody deserves to be 'pigeon holed', but everyone can work towards understanding each other.
I'm an ENTP, but in group situations I tend to shift into INTP or ENTJ. I'm most at home playing second fiddle to a strong leader whose direction I respect. I can be a dictator, a recluse, a workhorse, or a cheerleader. What I cannot be is content when I don't see the point of activity. That's NT all the way, which isn't the easiest way (or the most flattering, necessarily). You may have to buy and read Kiersey to get what I just said, but I hope you'll get this much at least: Understanding those things about my self is the spark, not the purpose. Self-analysis isn't the goal. Recognizing patterns of interaction with others can be a heartbreaking challenge. Now, welcome to the rest of your life.
Knowing one's Type isn't an excuse to avoid change. It's a roadmap to embracing the challenge of interacting with others not-like-oneself. Tendencies can also expose weak areas. Thus, like so many things, personality study can be an opportunity for God. For a Christian, "knowing thyself" should bring one afresh into Romans 7. And then, hopefully, Romans 8.
People who resist personality study may be innocent cynics. They may also prefer to continue enjoying their current delusions. Most folks would rather keep thinking everyone else has the problem. Heh. Heh. Sigh.