This article does an excellent job of explaining the issues involved in picking someone to head the Census Bureau.

• Census Pick Illustrates Broader Obama Strategy, by Michael J. O'Neil, The Huffington Post, June 15, 2009.

If you need a non-statistician's explanation of why sampling and estimation is as accurate as an actual enumeration, consider your last blood test: did they remove and test ALL your blood?. These matters are beyond any scientific dispute. Yes, sampling is theory -- the same way gravity is theory.