Really... why do they all do it when they demonstrate it then?
http://www.youtube.com/watch?v=fdr-ChfedUM
http://www.youtube.com/watch?v=rWvya9MVhjs
http://www.youtube.com/watch?v=ndY4jMB9w6U
http://www.youtube.com/watch?v=vI7VvZmIDBs
etc, etc, etc...