ChartsBin.com has a great flash animation on a page titled The Largest Oil Spills in History, 1901-Present.
Check it out if ever you need to get an idea of the amount and placement of some of the largest oil-related disasters (aside from war) that the global ecology has had to endure.
These spills have an impact not only on any local environment affected but also on any systems that the pollutants pass through as they are dispersed far and wide through the ocean.
The current huge gusher in the Gulf will leave an ecological wound that will impact not only the local communities, but also other ocean-based life -- even if the oil remains relatively close in proximity. [more on affected species] And we already have plenty of indicators that "close proximity" is highly unlikely, with some predictions stating that the oil (including all the accompanying toxins and chemical dispersants) may ride the Gulf Stream for a trans-Atlantic boost to start impacting far-off places like Norway. The more conservative estimates range from only affecting shores along the inner gulf to tainting shores along the eastern US seaboard.
It's not just oil itself that we have to worry about with regard to polluting our environment. We have, as a species and particularly as a culture, often regard ourselves as masters of our environment, not subject to or impacted by it, the occasional wild storm tornado, earthquake, fire or flood notwithstanding. Our habits and self-importance have led to an arrogance and disregard that is getting more difficult to ignore as our everyday overconsumption begins to stress, strain and compromise a variety of systems. The impact of our negligence is becoming more difficult to ignore, too. [pacific gyre, domestic drilling, mountaintop removal]
As a parting thought, here's a little something to think about: how much of an impact on our environment do we have simply in pursuit of pleasure? Here's a question and answer that may bear some further investigation, as well as some somber thinking:
Now, I'm off to go wobble der wooblekint ("walk the dogs" in warped English-Germanesque).