Black Friday 2011

History
That the day after Thanksgiving is the "official" start of the holiday shopping season may be linked together with the idea of Santa Claus parades. Parades celebrating Thanksgiving often include an appearance by Santa at the end of the parade, with the idea that 'Santa has arrived' or 'Santa is just around the corner'.
In the late 19th century and early 20th century, many Santa parades or Thanksgiving Day parades were sponsored by department stores. These include the Toronto Santa Claus Parade, in Canada, sponsored by Eaton's, and the Macy's Thanksgiving Day Parade sponsored by Macy's. Department stores would use the parades to launch a big advertising push. Eventually it just became an unwritten rule that no store would try doing Christmas advertising before the parade was over. Therefore, the day after Thanksgiving became the day when the shopping season officially started.