Top 10 Largest Databases in the World

One of the Top Ten Lists You Don’t Want To Miss from Jim Calloway’s Law Practice Tips Blog caught my eye: Top 10 Largest Databases in the World. Number 1? the Library of Congress.
The post didn’t give any sources for this information, however, which makes me wonder about its validity. I’m a librarian – I like to see sources.
For an interesting comparison, see the Sixty Largest Deep Web Sites as of 2001 in BrightPlanet’s Deep Web White Paper (table 2).