I might seem late to this party but that's only in public. I've harboured suspicions for a few years that penal substitutionary atonement theology is wrong. After a lot of thought on the matter I've decided to come out of the closet as a skeptic.
We know it in its most famous form as a derivative from Anselm's Cur Deus Homo. For me I think its most famous form is in any number of evangelical tracts (thank you especially to Jack Chick) and the altar calls so common in pentecostal churches and tent revival meetings. Ostensibly derived from Romans but conveniently ignoring the other New Testament authors, it's a popular explanation.
But here are my suspicions.
It's nothing like the message of salvation in Acts. Throughout Acts the disciples preach that salvation comes when one believes that Jesus is the Christ so that one's sins can be forgiven. Note that this is "forgiven" and not "paid for."
The entire pistis christou debate (on which I side with the subjective genitive interpretation) either requires faith in Jesus or rests on the faith of Jesus, neither of which indicate substitution.
In Romans, sin enters through our participation in Adam and our salvation enters through our participation in Christ's death. Participation isn't substitution either. Adam's sin better not be known as penal substitutionary guilt theology.
Even in Hebrews, where Jesus' death is most explicitly compared to a Jewish substitutionary atonement sacrifice, the sense to me is that Jesus death is better but not by magnitude. It's not as though there's a quantitative difference between a goat sacrifice and Jesus' death (i.e., a goat balances the sins of a nation and Jesus is like a super-goat who is able to balance the sins of so many more), rather there is a qualitative difference between a goat-atonement and Jesus' death.
Let's not go much further for now. It's enough to say that the penal substitutionary atonement account has its problems. And let's face it, it was only developed in the late 11th century. For more than a millennium Christians believed something entirely different about Jesus' death. It's been around for less than half the life of Christianity and like most Christian teaching is open for debate.