Prof. Barro of Harvard has written an article in the WSJ on the multiplier effect, or lack there of. Bottom line is that government stimulating spending will likely raise the GDP by less than the increase in government spending.

Even without a multiplier larger than 1, government spending could be the least costly way of arresting the economic fall. I have issues with how this stimulus seems to be re-inflating the bubble that got us here in the first place.