There's a video making the rounds of the 'net, purporting to show the results of oily rain falling on Louisiana. I don't know that it's not a hoax although if it is, it's well done. The explanation it seems to put forth -- that oil has been carried up into the air by evaporating water and formed droplets -- makes no sense at all.
In truth, I wish it did make sense. If that were happening, it would make an incredibly powerful "everything really is connected" case study.
But even if the "evaporating water" explanation is entirely false, I'm hoping the video can still be used for teaching purposes. My guess is that the source of the oily rain (again, assuming the whole thing isn't a hoax) is oil in aerosol. Tiny oil droplets suspended in the lower atmosphere that get washed to the ground when good old normal rain starts falling.
That aerosols are formed is a foregone conclusion -- the widespread smell of oil, and the respiratory and other problems experienced by recovery workers clearly indicate that oil (or components of oil) is spreading as a vapor of some sort. And it's easy to hypothesize (I don't know of any data which indicates for or against) that the application of dispersants likely speeds aerosol formation (plus adds more chemicals into the mix).
If that line of thinking turns out to be anywhere near correct, then the "raining oil" video becomes a powerful tool for communicating the idea that "there's no place called 'away'." The dispersants don't make the oil go away. They just make it different. Less obvious, perhaps, but not necessarily less damaging. Take it up one level in abstraction, and maybe we even get to the concept that to every complex problem there's a simple and obvious "solution" which just makes it worse.
It will be years, probably decades, before we have anything like a comprehensive model of the effects of this disaster. But if we're sufficiently honest about what we don't yet know, maybe we can still use it as a teaching tool.