Canadian Sweepstakes Winners

<<To be declared a winner, any Canadian resident selected in the drawing will be required to correctly answer without assistance of any kind, whether mechanical or other, a time-limited mathematical question. The question will be administered by telephone at a mutually convenient time. >>

I have seen this often in sweepstakes rules and never understood what the point is.

  1. why?
  2. how hard is the math question?

I am not Canadian, but this really seems stupid. Can anyone enlighten me?

http://boards.straightdope.com/sdmb/showthread.php?threadid=81510