TragicWhiteKnight: There's two important factors on this topic that have been overlooked despite being 4 pages long, being utterly obscured by unnecessary braggadocio. While there's certainly truth in jonb & Icarus' ideas, there's also a question of exposure (no terribly poor pun intended) - penis size is by and large (again, no pun intended) a private matter (could private be a pun on 'privates'? Either way, no pun intended).
1) Opportunities to see men nude, especially well-hung men, are pretty much limited to areas which show no sign of academic learning (until they open up a MENSA sponsored nude beach, anyhow). 'Professionals' like porn actors or (to a lesser extent) strippers will be assumed to be dumb because of the lowliness of their profession [not the bad quality of the script] (otherwise, they'd have a real job). Similarly, guys at the gym are more likely to be bodybuilders than scholars (yes, you can be both, but there'll be a majority of men concerned with their bodies not their minds, regardless of natural intelligence); consequently those who've put more effort into their bodies are going to be the one's most willing to show them off at nude resorts, or via casual sex.
2) In cases where penis size is given without sight, this can be seen as a breach of social convention - i.e. a lack of social intelligence. By this, I mean that for a man to reveal his cock size in the course of everyday conversation, especially attempting to use it as a way to impress girls, would be seen as pretty dumb and ignoring the fact there are plenty more important things. This situation is multiplied over the Internet where some (believe it or not) guys lie about their penis size; these people help give the well-hung a bad name.
