Myers-Briggs is complete bullshit, no better than horoscopes, numerology, or tarot.

Have you ever read through one of the MBTI type descriptions for someone other than yourself? I have. I've read through many of them, and just like horoscopes, they all sound like they accurately describe me. They all fail the same simple horoscope test that James Randi gave to that college class on his Nova special (everyone rates their horoscopes as being 99 percent accurate, only to find that the entire class was given the exact same horoscope reading).

From the Skeptic's Dictionary Entry on MBTI:

The people at CPP aren’t too concerned if the list doesn’t seem to match your type. They advise such persons to see the one who administered the test and ask for help in finding a more suitable list by changing a letter or two in your four-letter type. (See the report CPP publishes on its Web site.) Furthermore, no matter what your preferences, your behavior will still sometimes indicate contrasting behavior. Thus, no behavior can ever be used to falsify the type, and any behavior can be used to verify it.

Keep in mind that this is based on Carl Jung's concepts, a man who believed in some pretty weird and unscientific shit.