This 7 - 1/2 minute video by Reason.tv takes a look at why the $840 billion stimulus package signed into law back in February of 2009 failed.
Also, this from the CBO:
The Congressional Budget Office on Tuesday downgraded its estimate of the benefits of President Obama’s 2009 stimulus package, saying it may have sustained as few as 700,000 jobs at its peak last year and that over the long run it will actually be a net drag on the economy.
CBO said that while the Recovery Act boosted the economy in the short run, the extra debt that the stimulus piled up “crowds out” private investment and “will reduce output slightly in the long run — by between 0 and 0.2 percent after 2016.”
If you are scoring at home, that's $1.2 million/job "sustained"... whatever that is supposed to mean.