Felix Salmon has made a big splash with his argument that now is a good time to sell stocks because they're volatile. My first instinct is to say that this doesn't much matter for people under the age of fifty. As long as you're putting a consistent amount of money in your 401(k), over time, it won't matter; you'll get more growth than bonds, and even though the market moves around, what you lose on the swings you'll make up on the roundabouts. You'll probably need to give more attention to when you should start shifting your portfolio towards bonds than you would in a less volatile market, but in the meantime, you'll still enjoy the benefits of growth in the stock market.
That presumes, however, that there's still a substantial equity premium--which is to say, that stock returns will, on average, substantially exceed the returns on debt. That assumption is based on 100 years of evidence. But just because something was true for 100 years, doesn't mean it will be true forever.
In fact, stock prices have the odd characteristic of many financial assets: if everyone thinks that something is true, then it's no longer true. Efficient markets types tell us to invest in indexes because you can't beat the market--but if everyone invested in indices, the market wouldn't be efficient, and you could. Portfolio theorists tell us that investing in a broad portfolio of stocks will yield a substantial annual return in excess of the return on US treasuries--but if everyone believes that stocks aren't really much riskier than bonds, then they'll bid up the prices until there's little excess yield.