The annual Mummers Parade and the 2008 Phillies Championship Parade come to mind as the only comparable events for the ridiculous amount of foot traffic South Broad Street saw this past weekend.  Enlarge the image above, and see how this multipurpose arterial was really put to the test, all within a 24 hour period!

The area covered by a person standing still is approximately three square feet (3 sf).  Note the spacing difference between marathon runners:

and a festival crowd: