Oh, people who divide everyone in 2^N classes.
I remember one fellow student tried to classify me.. He said that my being in a random place between some of the categories shouldn't be possible, but agreed that it apparently was.
Of course, creating middle ground on every question resolves every problem you can have with classifications except applications of classification.
Not everyone is black, white, or gray; some of us come in blue and orange.
While psychology wonks have been going on for years about the statistical rigor and calibration of the Big Five, most people have just carried on using the Myers-Briggs type indicator (MBTI), which may not be statistical or scientific but is able to categorize people without insulting them.
A serious critique of the MBTI is the Myers-Briggs entropy distribution paradox (or, "Why are there 16 personality types when everyone I know is an INTJ?") A new personality test which has been gaining ground recently, the MLPTI, does not break up the INTJ into multiple categories; but does reduce the number of bothersome non-INTJ personality types and thus ameliorates the entropy paradox. For those not yet familiar with it, here is a rough translation between MLPTI and MBTI types.
The loss of half of the MBTI categories is not a serious problem, as demonstrated by the fact that you can't even name the ones that were left out without going back and looking. Seriously, when was the last time you met an ENTP?