I'm reading the book, Farewell to Jehovah's Witnesses, by John Rippon. I'm convinced that some of the things that keep the Witnesses in tend to turn, over time, into the things that drive them away. The ritualistic shunning of family members and friends, the constant bombardment of the same things over and over, the relentless expectation of Armageddon and the forced separation from the world; these all create a steady pressure that, over time, starts creating cracks in their own foundation. To some degree this is offset by the granting of recognition and power; however, there is a great deal of mind control at work that I don't see in any other Christian religion.
Some who fall away from the JWs become atheists and reject all religion, having been burned. That also is part of the mind control process, though they don't realize it, because the scriptures they once knew (and misinterpreted) become hateful to them. I also think the translation of the scritpures they use is so pedestrian and esoteric that it goes out with the bathwater.