Pirates of Penance

I was listening to Led Zeppelin Four (Runes) today at work, and the part in "Stairway to Heaven" about buying the stairway to Heaven made me think of their dig at the sale of indulgences by the Roman Catholic church. I don't remember the name of the guy that sold indulgences who got under Martin Luther's skin, but it was enough for him to make a big stink about it.

This got me thinking of how you can buy carbon offsets now. What makes them any different than indulgences? And who will be this generation's environmental Martin Luther, propounding a heavenly environmental grace?