I would take personality tests with a half-grain of salt, but I suppose if enough people take them, they assume their own reality and affect your employability (like IQ tests). I am an INTJ, whatever that means. There's probably some malleability to the categories.
It should come as no surprise that nearly all workplaces desire the outgoing, social, and smiling. I am none of these (smiling is easy enough, except for my coffee-stained, choppy teeth). I lost the ability to interact confidently in adolescence, and after 15 years doubt that it will ever come back. I'm sure most of us here are aware of being screwed over by our personalities. I've come to think of them as prisons.