While it is fast, it certainly is not unheard of or something that is many of have not seen before.
If you take a video from a racing quad and speed it up both the video and especially the sound makes it very obvious.
Seen a lot of leghbthy discussion on this video, the final conclusion is almost always that it must be real. However there is one spot where it looks like an almost super sonic bird goes by, it is likely a fly or Kant flying right in front of the lens.
My opinion is that it does s real, you can ask the original author about it on facebook if you'd like his input.