Differing Data Centers reporting differing SERPS .During this time SERPs (Search Engine Results Pages) can fluctuate and websites often see a surprising rise or fall in rankings before returning back to normal.

very true

Google dance refers to the period of time when Google indices are tuned. This will often cause both a fluctuation in index size as well a significant change in a web site's search result position.

Yeah! Wikipedia always have good information about any term.

Want to see Google Dance 2005 - check here - http://www.google.com/googledance2005/

GOOGLE DANCE has often been used to describe the index update of the Google search engine.

Google Dance is inevitable so we as marketers can't do anything about it