In my early 30's, I was 'called' to be part of the Stake Relief Society - which is the group for women from 18yrs and up.
I was researching a teaching assignment in a mormon church library and came across some information that was totally opposite to what the church had always taught me. The more I looked, the more I found, and the more disturbing it all became.
I eventually used google to research Joseph Smith, found he'd been convicted for fraud (the court record is online), and that the history that was taught me was untruthful. It then snowballed, and when I spoke of my concerns to my bishop, he told me to stop or I would be excommunicated. He even quoted a church leader to me "That which is true is not useful".
I then discovered that in order to stop being a member, I couldn't just stop attending church, I had to formally resign - which I did, but the church dragged their heels and it took nearly a year, and eventually a lawyers letter, to get confirmation of my resignation.