Barton Biggs

The S&P 500 has nearly doubled from its post-crash lows, and small investors are finally getting off the sidelines again. Normally, that would be a danger sign for a correction, but right now, all signs point to the upward stock market trend continuing in 2011. Here's why:

A supposed truism on Wall Street is that betting against the crowd is always a wise move. And these days, the crowd is decidedly bullish. Yes, that's often a sign that the end is near. But right now, a good argument can be made that things will still get better.

Big money managers can change their strategy at any time. But for individual investors -- who are betting their own money -- the decision to be bearish or bullish is much tougher. Here's the key question: What lets you sleep at night?

Traditionally, doomsday prognosticators came from the fringes of society. But some of the direst thinkers are now on Wall Street, where fear and foresight have some money men contemplating their escape routes.