The Google dance occurs as Google indexes each server.

 This is done on one server at a time because if all were indexed at the same time it would cause a complete shutdown of the Google search engine each time they had to index. Just think how much business Google would loose. When 2 big sites are on separate servers and linked together this will cause the dance effect as the Page Ranks go up and down.

So why all the panic:  when web masters see their sites going up and down in position they naturally think that they are going to lose a lot of sales to competition. However this may not be the case as your competition is facing the same problem.

Here are some ways to stay clam and on top:

-Keep all your options open by indexing all your pages on Google. By doing this you can cover yourself as if one or two go down in position the others may still stay on top and be seen.
-Add content on a regular basis-perhaps once a week- this will keep Googlebots interested in your site and keep you on top.
-Check that your keywords are still being searched for and popular
-Use isolation optimization. 1-2 keywords per content page and 3% density
-Make use of RSS feeds and blogging this can help new content be indexed better
-As always be careful whom you link to.
-Use multiple promotions Google should not be your only source of business

Now the small monthly dance is not too bad the worst Google dance occurs when they have to adjust their algorithms. This does not happen to often but when it does the dance becomes frenzied. Positions move up and down dramatically and webmasters are in an uproar.