This video is not a prank. What you are seeing is a self moving Nokia Lumia 920. It is NOT due to vibration. It is making its way to the edge slowly. In fact, I think the term to use is “sliding”. The phone is sliding across a flat surface.
According to WP Central, the logical explanation seems to be due to the fact that the surface of the Nokia Lumia 920 is super smooth. It is so smooth that any slight incline (maybe not detectable by naked eye.) will cause it to slide.
Check out the video.