I knew an elder and his wife who left. There was a talk about apostasy afterwards, so I assumed that was why they left. No one talked about them though, and I was afraid to see them around town because I thought they were evil. I can't remember if they left 8-10 years ago? No one else left the hall at the time.
They had a question about the UN issue, and the elders never got back to him and just DF'd him and his wife without them knowing. I asked my sibling who was friends with the couples daughter why they left after listening to a Steven Hassan video last year. He said "they must have had a good reason," and that made me wonder.
Growing up, the majority of kids left the religion after they gradutated. I questioned why so many left, but rationalized they must have been "weak." Then my sister left 3 years ago. I would get depressed and wonder why such a good person would die. I also wondered why most of the people who left the religion were so happy, and why the witnesses in my cong. were so dysfunctional.
I would say personal experience made me question things, and the apostates on the Internet helped me deconstruct my beliefs and realize it was all a lie. Seeing an elder leave was something that stayed in the back of my mind, but I needed to be ready to investigate my doubts first...and that took 10 years!