[HighlyOpinionated]

Here’s proof that it’s much closer to 2 Million than half a million.

http://moderateinthemiddle.wordpress.com/2009/09/12/aerial-views-added-d-c-police-close-roads-to-buses-people-on-footestimate-1-2-millionl-abc-cant-count912-party-on-patriots/

[SeattleBruce]

http://moderateinthemiddle.wordpress.com/2009/09/12/aerial-views-added-d-c-police-close-roads-to-buses-people-on-footestimate-1-2-millionl-abc-cant-count912-party-on-patriots/
++++++++++++

I’m not sure yet how many came. It was a LOT! :)
This link you provide, has probably the best aerial shot I’ve seen yet. Wow, the number would only vary somewhat based on density - but clearly, it was in the 500K to 1M mark, by looking at the mall graphic.