Take a look at this. It looks like we got fooled.
http://www.youtube.com/watch?v=n1UEv2PIzl4
At the 2 minute 35 second mark of the video the flag is still. When the astronaut goes past it, it starts to move.
There's an analysis of it here at the 3 minute 5 second mark.
http://www.youtube.com/watch?v=rC1legw5-gs