Illusion
A wild illusion. The spinning silhouette mostly starts up clockwise for me.
Update (10/14/07): Lots of comments over here at Marginal Revolution. There is a reference to left brain versus right brain dominance, etc., but I'm not too sure ... I like the comment about the person that tried filming it backwards ... then when played backwards, the person still saw things going in the same direction. :)

I could not get her change directions at all ...
Posted by:Zoli Erdos | October 14, 2007 at 07:35 AM
It started counter-clockwise for me. May be I am too singleminded...
Posted by:Phil | October 17, 2007 at 07:58 AM
Geez I can't get it to change directions! Maybe I didn't try it hard enough.
Posted by:Jay | November 08, 2007 at 09:25 PM
I can't get her to spin in the other direction either. Is it supposed to say something about me? Does the right brain - left brain explanation stand or did someone just decide it had to be that because they couldn't think of anything else?
Posted by:TITC | December 07, 2007 at 04:32 AM