Those who leave the Watchtower Organization leave for two reasons: fleshly and intellectually. The fleshly group are the teenagers we saw in our halls getting involved in drugs and sex and getting disfellowshipped. They were already hanging out with "worldly" people and were never into the organization enough to expose the lies in the first place. Most people in this group still believe the witnesses have the truth, but they just don't want to live up to the "moral standards" the church demands.
The second group are the ones who left for intellectual reasons. A lot of us were much farther into the religion than the first group. We were the "goody-two-shoes" witnesses, the ones would would rat out our friends if we knew they slipped up. Like faithful little lambs, we avoided "worldly association" like the plague. We wrapped our entire lives into the witnesses, either because we were once convinced of their arguments or born into the religion. When we became disillusioned, our world literally crashed in on us. We had no friends, and our relatives cut us off completely. If that wasn't the case, we started a fade that went on for years or is even still going on. We let the society destroy our social skills and trap us. We're damaged and we need support. I don't mean to sound judgmental, but a lot of the people who don't post on these boards quite frankly had an easy time leaving. They already had a social network and friends. They assimilated just fine. They're a different breed of ex-witnesses and don't need support like we do.
That said, I don't mean to sound like I'm pigeon-holing everyone's experience into these two categories. Obviously there are people from the first group on this board, and people from the second group that aren't. But as a general rule, I think this holds true.