Brickset members own 1 BILLION pieces
Just six weeks since we, as a community, owned a combined total of $100,000,000 worth of LEGO (see this news article), we now own at least 1 BILLION pieces of LEGO between us!
Given that it's shared between the 44,600 people that record their collections on the site, that's an average of 22,400 pieces each!
If we assume that the average height of a piece is 10 mm (roughly the height of a brick) then if we were to stack them all on top of each other, it would reach a height of 10,000 km. If we assume that the average width of a piece is 15 mm (roughly the width of a 1 x 2 brick) and we were to lay them side by side, they'd reach 15,000 km which is more than the diameter of the Earth (12,000 km) and about 1/3rd of its circumference.
According to Wikipedia, LEGO estimated (in 2008) that it has produced some 400 billion parts in total. Annual production averages approximately 36 billion per year, so the total made to 2012 is something like 600 billion. Our total then, is around 1/600th of the total ever made.