I see your point, and agree, but I think there is reciprocation. While SDN is a self-selective community (in who joins, who posts, and who discloses their scores), I think the advice available here also plays a role in helping some members achieve good scores.
I look at myself and my two good friends I mentioned... if I were not an SDN member, the three of us would be pretty lost for board review. No one else has given any of us the type of advice available here. About the best we would have is "get step-up or FA or something like it, and there are some audio path lectures out there, and probably get the Kaplan books or course."
I think the Kaplan part would be the only thing saving our hides! I would have never heard of Goljan, or RR path, or the 1999 HY cell/molec book, or CMMRS, or known that BRS physio is fine (even at a quarter the size of the Kaplan physio), etc. etc. etc. Those resources guarantee nothing, but I wouldn't have even heard of them. I would have done like many of my classmates... walked into our book store, and on advice of the lady there purchased step-up. And then perhaps bought a load of used review books having no real clue which ones were worth the time to read. Boards would have been a big mysterious black hole looming on the horizon, I would probably not have had any idea of a reasonable study plan, and thus would not have organized and managed my time nearly as well, and ultimately would have been much less prepared than I will be. If I manage a 200 now, I would have probably failed without SDN.
It is sad, but I know many of my classmates who think Kaplan is just making money off students and doesn't teach them anything they can't teach themselves (they are right, about that last part I mean), and think that reviewing class notes and buying step-up is going to get them an average or better board score (I hope they are right).