1. A personal crisis.
2. A let-down by the church.
3. A questioning of his or her world view.
For me it was a total reversal of this order. I began to question my world-view, followed quickly by my church letting me down by failing to understand the honesty of such investigation. That resulted in a crisis - of my faith, which is pretty damned personal IMO.
My faith was shaken first in the Watchtower, then in the Bible and Christianity in general [the Watchtower and the other churches are in my opinion just two eggs in the same basket], then religion.
I am now a happy, sane, atheist. Quite simply stated: I just prefer reality over fantasy and little invisible friends who live in invisible places, who make everlasting promises and invisibly 'inspire' them to be written.
And yes - without the internet I might have eventually left the Jws and later Christian insanity - but it would have been much harder to pull all the information together to do so. I would probably have 'left' - but would still be sitting on the sidelines riddled with guilt, thinking it was the 'truth'.
Jeff