The Missing Oil?
Some back-of-the-envelope math on the Gulf spill: roughly 102 million gallons of oil and about 1.1 million gallons of dispersant, against a Gulf volume on the order of 650 quadrillion gallons.
Run the ratio and the spill comes out to a vanishingly small fraction — parts per trillion. No wonder they were having trouble finding the oil to clean up. (Scale matters.)