Benford’s Law tells us that

“in listings, tables of statistics, etc., the digit 1 tends to occur with probability of roughly 30%, much greater than the expected 11.1% (i.e., one digit out of 9)”.

This can be useful in detecting whether a dataset has been tampered with. Kottke applies this to tampering with blog timestamps.

Benford’s law has a wide variety of applications, including detection of tax fraud, voting fraud, “curb-stoning” in surveys, and data integrity in databases. I touch briefly on some of the uses in my web site.