[OwenKellogg]

Don't know if either of these were working for Beck, but someone was observing and documenting the crowd from above.

[CedarDave]

That balloon is likely the one used by the company (AirPhotosLive.com) that CBS hired to make the 87,000 estimate.
http://www.cbsnews.com/8301-503544_162-20014993-503544.html