Mystery Solved

Solved in the sense that the bee activity has an official name, washboarding.
Named but no one knows why the bees do it.

Here is the response from Dave of the Backwards Beekeepers :

Found this on Michael Bush's site:

Why are they dancing at the entrance in unison?
A few times a year some new beekeeper wants to know what the bees are doing line dancing (rhythmically swaying) on the landing board. This is called "washboarding" and actually no one knows why they do it, but they do. Personally I think it's a social dance. Perhaps even a thanksgiving dance.

Beesource has this interesting thread on washboarding:

http://www.beesource.com/forums/showthread.php?t=230659&highlight=washboarding

Many theories but no definitive conclusions. Another mystery of the wonderous apis mellifera :).

So it was not moon walking. As an added note, i did not see the bees doing their usual daily orientation flights on the day of the dance and some were still dancing an hour later.
Thanks for the info Dave.