Jeremy Frank at Letters from Babylon briefly touches on the question of whether the concept of free will is compatible with the concept of eternal security. He argues that it is, even though he's a Calvinist and thus doesn't feel much need to make that argument.
I've always been an advocate for free will rather than predestination myself, although in recent years I've begun to wonder whether this is one of those doctrinal disputes where both sides are equally right, in that they aren't at all. I won't go into that right now (you may consider C.S. Lewis's Mere Christianity, Book 3, Chapter 4, "Morality and Psychoanalysis," for one of the ideas that is shaping my thinking in this), but I will make this tricky question even trickier.
I've always thought that it makes more sense to consider God outside of time, unconfined by its constraints, and that His view of us is not a linear one. We humans tend to think of our lives linearly: we go from point A to point B, and that leads us to the conclusion that when it comes to your relationship with God, it doesn't matter where you've been for most of your life, what matters is where you are when you die. That's what really counts. And so the criminal who stole and raped and murdered, if he repents on the way to the electric chair, is saved. What of the minister, who preached and cared for the sick and loved his neighbor, who at the end of his life finds himself in poverty, loneliness, and despair, and in his twilight years loses his faith and dies in bitterness? Do we give him up? Does God?
If God looks on our lives as a whole, does He view our salvation as a turning point, as we do, or as a high point? Is faithlessness and disbelief worse for being on one side of that point than the other? Here's where I'll run counter to my own argument and say that it is, since from our point of view, our linear point of view, it is worse. If a child takes a toy from a store without understanding he is stealing, we don't see it as a crime. If a teenager does the same thing, we do, not because the teenager is older, but because he knows better. Rejection of God after salvation is worse than rejection before not because it's on the other side, but because before you didn't know God to reject Him, and now you do. But if God sees our lives as a whole, is that much worse crime of rejection by one who knows Him enough to negate earlier faithfulness? We might consider it so, but then, we live linear lives, and to us the rejection is more recent than the faithfulness. If it is no more recent to God than the faithfulness, then would He see it the same way?
Okay, that's enough making hard questions harder for today.