Interesting possibility... to me, the idea that it might be balanced just right for such behavior is more interesting than spooks or pixies... and more likely (although not very).
But...notice that the clip begins with someone touching it. And the other two swings are moving quite a bit.
Also: the video does not go on for ten days, and I have yet to see any swing in good repair go unused for ten days, so I really doubt that claim.
Then there's the fact that it's from the Sun... just in time for Halloween... ::)
i dont know rotty... if i were a little kid i would not be likley to sit down and start swinging next to a swing that was swinging by itself! ;D regardless of whether or not it was in good repair