Hi friends,
one month back i uploaded a video and after two days its in first of google for my keyword and two weeks later its in 16th page of google and later its again comes to 7th.

My question is, does google do a dance for ranking videos? Or did I get smacked?
Many thanks in advance for replies.

 HI
fresh content is always at top, but as the time passes traffic reduces and may be reduction in viewer is one of the reason drop in ranking.

Hey, hang on! Its just a month. As for Google dance, it is over for good.
Just like a new website, a new video fluctuates initially. Also, video ranks is determined by the amount of views and likes that your video has.

A good on page (video tags, keyword in the title, description box, tags etc.) and off page (having a ton of views, likes and subscribers) might help you stabilize your video rankings.