Democrats are relying heavily on the claim by Moody's Analytics' chief economist that 400,000 fewer jobs would be created (and saved?) by the end of 2011 -- and 700,000 fewer jobs by the end of 2012 -- if Congress were to cut $61 billion. Now, the Moody's forecast has been battered by a number of economists, and Federal Reserve Chairman Ben Bernanke, a fan of stimulative efforts, dismissed those numbers, as well.
Who knows? Laymen like me can only rely on one scientific truth when it comes to economic forecasts: They're always wrong, except when by some fluke they're right.
http://www.realclearpolitics.com/articles/2011/03/02/stop_crying_and_start_cutting_109085.html

My favorite economists never make predictions like this anyway because they know what Harsanyi says - no ones knows what the future holds.  Why?  Because no human has enough knowledge to make a prediction.  No human CAN have enough knowledge for accurately forecast.  It's almost like we were not designed to understand, control and run economic processes on a world wide scale .... (yes, that's sarcasm)

This is what Hayek meant when he summed it up so beautifully: 

The curious task of economics is to demonstrate to men how little they really know about what they imagine they can design.
F.A. Hayek, The Fatal Conceit

This doesn't mean that folks don't make lucky guesses.  However, the fact that no one has ever made all the right guesses, or even the majority of right guesses, is the proof of Hayek's pudding.