Inspired by a comment exchange in Linguaphiles & Sesquipedalians I realized that the nature of the sensation of others being pretentious is a feeling that the other's theory matches up so poorly with reality that the poorness of the match is beyond a certain critical threshold.
Really, it seemed to fit. My first experiences with pretentiousness in others was with fictional character that had ridiculous interpretations of pieces of also fictional art. They, along with the pretentious people that I've encountered in real life, gave me the same sensation, and they both seemed to push reality away: The fictional art freaks would push away the fact that that piece of abstract art at which they were looking is devoid of meaning and that they didn't know at all what it meant. The IRL pretentious, in the case of creationists, for example, pushed away and hid from at every turn the fact that they don't know.
So what do you, the reader, think of this? Place your reactions to the headline first.