I think retention has always been a bit of a problem because the only hook newbies want is instant rewards. They can't see beyond that, and don't understand the value of networking.
You make a very good point about gamification to keep newbies hooked. I'm cooking something at the moment for newbies, but the gamification part is quite simple, I may look to beef it up in the next stage. Need to think about that after I launch it