I dunno - most staffed surveys (as opposed to self measure) put it closely around the 5.5 mark. This guy tries to take into account the fact that most "average" and small guys will run a mile from having someone measure their tackle, so when looking at averages you tend to get an average of those guys who aren't shy, which in general tend to be bigger. Also small guys don't put it about as much, so women don't tend to encounter them in the one night stand situation as often, not to mention that women aren't the best at guestimating size, and guys aren't always as honest as they should be.
A long time ago I was with a friends ex, my friend always maintained he has a large member - and having seen him in the lockeroom, I'd agree (I guess 6+ inches flacid), so when I was with his ex, I wasn't too shocked to here her tell me that he was big and about 8.5inches, but my jaw dropped when she said that I was far bigger and put me at about the 9.5 mark, in reality I'm nowhere near (at about 7nbp), and when I tried to correct her - she wasn't having any of it, so off went to get a ruler and prove my point (which written on here looks a bit wierd, but we were joking around at the time so it was all a bit of fun). She was still convinced I was bigger than him, but I just put it to confusion and forgot about it. Years later my friend starts an amateur adult entertainment site, and appears on there, it turns out his 6+inches flacid turns into about 5.5 erect (ie it doesn't grow in length just points upwards), he must have lied to her - and she didn't know any better. So I quickly learn't that a) girls don't know shit about size or measuring, b) flacid length really doesn't having any bearing on erect length. c) Guys lie - the strange thing is my friend really does think he's big cos of his flacid length (infact he's even said I looked small compared to his "big gun" - I guess he thinks my flaccid 4" equates to erect 4" - I just smiled and said "probably" ;-)...