LONDON -- It's an impressive list: CIA official Aldrich Ames jailed for life in 1994 for spying for Moscow; CIA agent Harold Nicholson jailed for 23 years in 1997 for the same offense; FBI employee Earl Pitts sentenced to 27 years later the same year for passing information to Moscow; U.S. Army Col. George Trofimoff charged last year for spying for the Russians for 25 years; and now senior FBI agent Robert Hanssen charged with working for Moscow for 15 years.

Assuming that only a fraction of the Americans with high security clearances who are on Moscow's payroll actually get caught, then the total number must run into the dozens, maybe even the hundreds. Which raises two questions.

One is why so many Americans want to spy for foreign powers. There is no suggestion that ideological sympathies had any role in the recent cases, so perhaps we should just put it down to the spirit of free enterprise.