Orin Zebest (flickr 2006)
Record for most people simultaneously doing the hokey-pokey:

4,431
On August 25, 2003, 4,431 people in Toronto danced the hokey-pokey for five minutes, a record for most people doing the hokey-pokey at one time. On May 16, 2009, people in Council Bluffs, Iowa attempted to break the hokey-pokey record, but attracted only a few thousand people.
Source: Omaha World-Herald, 5/17/2009

 
   
  Number of American square-dancers at the close of 2009:

300,000
The U.S Dancing Association estimates that the number of American square-dancers has diminished from over 1 million dancers in the late 1970s to just 300,000 in 2009.
Source: Wall Street Journal, 12/16/2009

 
   
  Origin of the Charleston dance:

Charleston, South Carolina
This peppy dance, symbolic of the Roaring Twenties, took its name from Charleston, South Carolina, where it was likely first introduced as a variation on an earlier dance originated by American Blacks. The word was first recorded in this context in 1925.
Source: The Facts on File Encyclopedia of Word and Phrase Origins, 1/1/2004

 
   
  Number of people employed as choreographers in the U.S. in 2006:

16,340
According to the Bureau of Labor Statistics.
Source: New York Times, 1/27/2008