First of all, you can't leave the faith. Once you're saved, you're saved for good. There's no way out. Secondly, why would someone want out? Some of the people on these sites professed to have been Christians for 40 years. What made them change their mind? I wondered about that, so I started reading.
Some claimed to have "left the faith" because of all the new scientific evidence. According to them, many of the miracles in the Bible were not miracles at all, and the knowledge that we have now proves it. For example, one person claimed that the maniac of Gadara was not possessed by demons but was simply suffering from a mental disorder or hormonal imbalance. They claim that Jesus didn't actually cast out the demons, but that He merely talked to the man and convinced him that someone cared for him which helped the man come back to his senses. Far-fetched, huh?
Others claimed to have "left the faith" because they found out that God really wasn't loving after all. They said that once they started studying the Bible, they discovered that God was an "egotist with a blood lust." They claimed He was violent and did not love the world as they had been taught.
Some "left the faith" because they didn't fit in with their church family. Some "left" because they finally realized how naive they were being to think that there was a God and that He cared about anything but Himself.
The list went on and on, and I became more and more angry. What in the world happened to these people? I admit that the Christian life has not been a bed of roses, but then again, Jesus never said it would be. In fact, in John 16:33, Jesus said, "In this world ye shall have tribulation. . ." Yes, life is tough, but that doesn't change the fact that Jesus is Lord and that He died so that we might be free.
Why am I telling you all this? Consider it a warning. There are a lot of false teachers out there. There is a lot of false doctrine out there. The devil himself is out there trying to deceive us into forsaking our faith in God. Don't heed these things. Know what the Bible says and stand firmly upon its promises. No, life is not always easy, but God is always God. He is a good God. He is a just God. He is a loving God.