For a serious answer to why people stop posting, how about;

22. The move to the next stage of their life.

I joined this board while in college because I had questions about The Godfather after having viewed it for the first time. I got my questions answered, but checked back in periodically when I had nothing better to do, mainly because I started participating in some of the fantasy sports leagues. I graduated college, got a real job, and now simply don't have time to spend pointlessly debating on some message board.

Newbies find this site primarily as a result of The Godfather, so I'm guessing many get their questions answered and leave. I doubt any of this club bullshit has anything to do with it. How could someone get offended by or judge someone they've never met before? The next post in this thread could turn out to be the most insightful, caring, and thoughtful idea you've ever read in your entire life, yet the poster could have written it while carving up his next door neighbor's children.