Nigeria has been devastated by oil for decades. The New York Times reports that an oil spill the size of the Exxon Valdez has happened every year for 50 years in the oil fields of Nigeria, with the oil gushing into sensitive wet lands. A recent article in The Guardian is even more devastating, saying that life expectancy has plummeted in rural Nigeria as the oil spills contaminate drinking water. Protest has been brutally repressed, epitomized by the horrific execution of poet Ken Saro-Wiwa in 1995. (Due to outrage at that atrocity, Shell finally paid $15M for its involvement, which was just one in a long history of human rights violations perpetrated by and for the oil companies.)
Like the Gulf spill, Nigerian oil spills don't just affect the local ecology. The oil flows out the Niger delta and into the Atlantic ocean. Also, over half of Nigerian oil wells are off-shore, and they're no safer than the ones on land.
Mexico had an oil spill in 1979-80 that held the previous record (140 million US gallons) and was only surpassed by BP today, at least according to current official estimates.
Tankers have spills at sea all the time that cause barely a ripple of notice.
Chronic oil pollution activities such as degreasing docks has also been chronicled as causing major environmental damage everywhere that oil is shipped.
Years ago I read an interview with a deep sea explorer who said that tar balls litter the floors of our oceans.
(There are also natural oil leaks, like Bush Hill in the Gulf of Mexico, but they generally become part of an ecosystem: the oil and gas is eaten by bacteria, which are in turn eaten by things like worms and mussels. Still, they sometimes result in tar balls washing on to beaches.)