The imperial summit 2012 (G8) will not be held at Chicago. The organizers have panicked after the success of the Occupy Wall Street movement and have moved it to the infamous Camp David mansion, weekend residence of the almighty emperors... opsa, US Presidents.
It is still only 100 Km. from Washington D.C. but I guess it's rural enough to be easily controlled by police and military. Or so it seems.
Still Chicago is to held the most important military imperial meeting of NATO and ISAF (occupation army of Afghanistan).
Source and further discussion at Kasama.