Since the spill is not ongoing, and it's in recovery phase, it fades from headlines. This is true for every natural Disaster, from Katrina to tornados. nothing new here. But it also may be that the media are not interested in reminding us of bad stuff that embarrassed Obama. You can choose your answer.
It is still discussed, and the process of "clean-up" is still going on. It's just that so many things go on in this country on a daily basis - it's no longer a "major" issue - as is free contraception for lame-ass women who want others to pay for the prevention of their own possible pregnancy, furthering a "green "agenda that will put this country in the deepest hole ever, and Obama claiming that "next time" he will put things straight. Yeah - right. The so-called "main stream " media will tell you about absolutely everything you don't need to know, and absolutely nothing you need to. It's what they do. Watch Fox News. It's actually "news".
America, and the world itself has a tendency to have a short attention span on major issues, especially those that impact the environment because the damage is done over such a long period of time. The world is over approx. 4.5 billion years old, so if something happens over a months or even a years time, people pretend it's not happening if it doesn't directly affect them. If it's visual at that moment, and hot off the presses, then it's a relevant issue, but if it's about some airhead socialite, then people need to hear it and dwell. But it is still discussed but only minimally in mainstream media outlets.