2 Peter 2:17-22 (ESV)
These are waterless springs and mists driven by a storm. For them the gloom of utter darkness has been reserved.  For, speaking loud boasts of folly, they entice by sensual passions of the flesh those who are barely escaping from those who live in error.  They promise them freedom, but they themselves are slaves of corruption. For whatever overcomes a person, to that he is enslaved.  For if, after they have escaped the defilements of the world through the knowledge of our Lord and Savior Jesus Christ, they are again entangled in them and overcome, the last state has become worse for them than the first.  For it would have been better for them never to have known the way of righteousness than after knowing it to turn back from the holy commandment delivered to them.  What the true proverb says has happened to them: "The dog returns to its own vomit, and the sow, after washing herself, returns to wallow in the mire."
Apostasy it is possible. It would have been better for them never to have known the way of righteousness than after knowing it to turn back from the holy commandment delivered to them. This isn’t to say that it would have been better for them to have never been told. We must remember hell is a real place and ignorance does not save us from the fate of unbelievers. But it speaks to the fact that to go from faith to unbelief to turn our back on Christ after we have known is a great and weighty sin that is not without its consequences. I am not one myself to make much of sinful categories, which ones are worse than others. Sin is sin in God’s eyes and it all demands our death, and eternal hell fire. Yet god in his grace has given his son to die for us that we might be spared all that through faith in him. Yet, I do believe there are sin’s that somehow carry greater consequences for our lives. Perhaps it is in nothing more than the effect it has on hardening our hearts. Perhaps it is that having committed the sin there is a heavier price to pay for it in this world. Apostasy is a sin that should not be taken lightly. And it should not be taught that it is just “theoretical” or cannot happen. This is not the biblical witness to the matter. There is more than just this passage that shows that apostasy is real. And this ought make one question the rest of one’s theology if they have been taught once saved always saved. Or that “election” cannot be undone.
What irritates me is the willingness of so many to turn away from the faith so easily. Why do otherwise intelligent people latch on to the nonsense spouted by Dawkins, or Bart Ehrman? When it just does not make sense at all, not even from a secular view point. I don’t know, but it does sadden ones heart. Some people it seems just don’t want to believe.