Personally I believe that its the election time. Popularity of Obama is going down. They need something to increase his popularity again. They kept Osama alive to continue the war on terror & to establish an occupancy in Iraq. Now, Osama is dead. Obama gains popularity again & wins the election. Thats pre-planned.

I would suggest you to watch the two documentaries below. I don't want you to believe them either. But, raise a question before you believe anything. 
http://www.imdb.com/title/tt1645089/
http://www.youtube.com/watch?v=7E3oIbO0AWE