I can't say whether it's fear of shunning or fear of Armageddon what keeps a witness in; only you can say so. However, considering the article JWFacts mentioned first, for the sake of commentary I can say that, among the faithful of a religion that doesn't require (anymore) that you shun your sinning or excommunicated relatives, a.k.a. the Roman Catholic Church, many, many, many people stay in out of fear of death/eternal torment. As you know, Catholics believe they have souls that never die; the problem isn't so much death, but eternal torment in hell. Some people are afraid of death because they are not sure there is a God, and, like Blaise Pascal, think that they lose nothing if they (somewhat) follow the religion.
As to Armageddon, leaving the Catholic church means getting over your fear of eternal torment and, therefore, Armageddon doesn't really scare a Catholic. Or an atheist, for that matter. He has already accepted that he is only bound for the grave.
I guess that witnesses fear shunning more than Armageddon because shunning is a clear and omnipresent danger, while Armageddon is something that, er, is always right around the corner, right?