The Waste Management X-Prize.
$1 billion to the company that develops the best method for cleaning up LEO. :)
I will always be a Space Advocate, but moreover I'm a composite advocate of science, engineering and technology, especially when it comes to the betterment of the human species. It's about time mankind start to learn how our technical 'bells and whistles' can start improving life for ALL people, creating a more sustainable world for generations to come.