Here you go: http://www.freemoneyfinance.com/2010/11/the-truth-about-mark...

  Invest in S&P 500 ETF (SPY) starting at inception
  Growth of $100,000 from 1/29/1993-8/30/2010
  Buy and Hold: $324,330.15
  10 Best Days Removed: $156,354.12
  10 Worst Days Removed: $692,693.90
  10 Best and 10 Worst Days Removed: not listed, but very close to Buy and Hold (the green line in the chart)

Rob Bennett's followup comments are quite good, as well.