He's not the only one who has been cashing out over the last months. In my opinion, it looks like we are in for a correction if you look at the long-term historic logarithmic graph of the S&P 500's value.

http://finance.yahoo.com/echarts?s=^GSPC+Interactive#{%22use...

As Warren Buffet says, "Buy low. Sell high." Macrotrends affect stocks as a whole, which affect public companies, which affect advertising budgets, which influences Facebook's income.

I've been bitten before by assuming a bear market, pulling out, and then seeing things recover, so I'm much more careful now and have not completely pulled out. Large investors that really don't need those extra boatloads of gold they might get if they miss an upswing have been pulling out, though, to avoid risk.