Small Business and Job Creation

While the President and Mitt Romney are in dispute over whose programs will do the most to help "small business" create new jobs, they agree that it's crucial to creating jobs. But is "small business" really the employment engine they claim it is?  It's not even clear exactly what "small" really means, and there's evidence that age is more important than size when it comes to job creation. Are the candidates focused on real economics, or are they pandering to the obsolete American myth of "Mom and Pop" setting up shop on "Main Street."