BP, the oil spill, and the liability cap

So, I'm wondering.

The oil spill is now up to... what? About 60,000 barrels a day? Sure, they're collecting a bit of the oil, and setting fire to some of the oil, but the rest of it is ending up killing wildlife, habitats, and jobs. BP makes more money than God, so why is there a cap on their liability? Doesn't a cap just push the company to make the cheapest decision?

More to the point, what's cheaper - letting the oil spill run its course and doing the cleanup, knowing what it will cost them? Or fixing it? What if fixing it will cost more than the liability cap on the cleanup?

Considering that they've made decisions in the past that were the cheaper, not better, decisions, I'd be afraid to let them make a choice on this. (I'm sure we've all heard about the Three Little Pigs analogy and how it was used in a meeting discussing a decision they made.)