Not all oil washing ashore is from the BP spill
6/11/2010 at 5:04 PM
http://www.cnn.com/2010/US/06/10/csi.gulf.oil.spill/index.html
So BP may not be responsible for all of the cleanup. The USCG is finding that a lot of what's coming ashore in Florida is fuel oil, not crude oil. Fuel oil is what many big ships run on.
And oil has always seeped from the ocean floor naturally.