S&P 500 at Record Highs...and so is Margin Debt! And Implied Volatility is back near its Low...

The Motley Fool yesterday put up this chart on their website in an article titled "Margin Debt Paints a Terrifying Picture for the Stock Market",

And today Jim Grant tweets,

Margin debt is back to the 2007 highs, while the price of implied volatility of the S&P 500 Index is back near its lows.
— Jim Grant (@GrantsPub) May 2, 2013

Add these to your current list of risk factors of being long the U.S. stock market.