It's just profit taking. A normal reaction to rapidly improving market conditions. I've said this in some other places, and I bet someone's going to step in right away and say it's just crazy, but I think the Dow is going to get to 15,000 within the next 18 months. I say that not because of any economic news that's coming out, but what's happening internally to many companies balance sheets.
I've been going through dozens of annual reports recently and most of them are showing a similar trend of paying off older, more expensive debt with fresh, low interest financing. As a result, even without having more people to sell products to, these companies are showing improvements in net income because there is less interest expense to them. When Intel announced a 4x increase in income, I wasn't at all surprised by that.
So rising corporate income should start to get the hiring process booted up again, and then those people spend, etc., it's a big cycle that just restarts. I'd maintain a hedge in fixed income as the markets rise, at least 25% in a bond aggregate fund should be good. Take profits along the way but don't exit the markets completely, you'd regret that.