My Interpretation:
people always forget an important point as well, positive posts don't get repeated. period. If someone is doing well on a regimen, they don't post everyday saying, "hair is still thick guys." then the next day post: "still doing well, still doing well." But the guy that feels like he's having a bad week will post ten times a day trying to find some answers, saying "hair is terrible, propecia sucks." This creates a huge ratio skewing, you can't deny this no matter how cynical you might be about the whole hairloss issue.
Secondly, positive posts don't get responded to. I have tried to post my positive results countless time only to find them buried 2 days later. They just don't get replies, simple as that. So people reading the board over time see negative posts getting all the play and all the positive ones getting read by a few posters only to be drowning in a sea of newbie fury an hour later. Eventually, you start believing no one is getting positive results.
Thirdly, as you said, and disregard, people who have success ARE just moving on with thier lives. And they do leave saying, things are great i'm outta here guys! only these posts, like i mentioned earlier, get buried very quickly.
All these things skew the success ratio. This board is not the public. Propecia did a double blind study of over a thousand people with photos, personal interpretations and doctor's hair counts. Trust that. And don't fret too much guys, my hair is getting better by the day. I never lose any hair in the shower or any other time, but it has taken some serious patience on my part. granted these aren't miracle drugs, and it doesn't give everyone exactly what they are looking for, but they work very well for some. cheers all.