These were developed based off of Jung's work, etc etc. (here's the link on more of the history) They're used by the government, most psychiatric offices, and several colleges. I had it done twice by my college (once in 1997 and again in 2011) to check where I am in relation to career direction and learning methods. A lot of institutions are trying to abandon it as they feel it's not "scientific enough", but I've yet to find personalities to be scientific.

My boyfriend had created one of the more comprehensive MBTI tests on the web around 2005-6 that had the most accurate algorithm and percentage placement scores. He sold it a little while after that; I understand most MBTI test sites made within the last couple of years have taken most of his work whole onto their own. He was actually using it to see what personality types congregated in what areas of the world; he still kept all of the data, he just hasn't pored over it yet due to Life events since then. I might poke him into it ... ENFP's just need to refocus is all.