"The idea that a bell rings to signal when investors should get into or out of the stock market is simply not credible.  After nearly fifty years in this business, I do not know of anybody who has done it [market timing] successfully and consistently.  I don't even know anybody who knows anybody who has done it successfully and consistently."

And just for good measure, here's another:

"Anybody who goes into the market to make money specifically in 2011 should either be spanked or have their head examined. It's just too short of a period to predict, and it's a crap shoot."

-- John Bogle, Founder of the Vanguard Group