Lant Pritchett, the former World Bank economist, shares Mr. Guest's skepticism about the importance of the much ballyhooed microloans that help the world's poorest people to buy livestock or open a small business.

WSJ: Book Review: Borderless Economics

Lant Pritchett, of the Kennedy School of Government at Harvard, argues that faster global migration would bring huge gains for poor countries, exceeding the combined rewards offered by foreign aid, debt relief and trade reforms proposed under the Doha development round.

ECONOMIST: Too much or not enough?

Lant Pritchett, a lecturer in public policy at Harvard, sees his work consulting for Google.org's initiative to better inform and empower poor people in developing nations as "a thin end of the wedge" that will improve the way money already allocated for the poor is spent.

FORBES: Google.org Opens Its Wallet--A Little