One of the biggest - if not the biggest barriers - to leaving the organization is family ties - particularly immediate family (i.e., those living in your household: sons, daughters, mothers, fathers, mother-in-laws, father-in-laws). I know of no bigger barrier.
Therefore, it's relatively easy to predict who will face the most adversity in trying to leave. In the lead up to the mid-1970s, hundreds of people here in New Zealand studied and became witnesses. After 1975 came and went, these people had relatively little difficulty getting out of the organization simply because they did not have family ties to the religion. I knew many people who were disfellowshipped for all kinds of sins in the mid- to late 70s. The impact of the disfellowshipping on them was close to zero, simply because they had no family to punish them. Lucky escape!
The Watchtower - like all authoritarian systems - depends on family ties to maximise the impact of its punitive measures.