Via WSJ (subscription only):

The number of millionaires in the U.S. increased to a record last year, boosted by gains in stocks and global financial markets, according to two new studies.

The number of U.S. households with a net worth of $1 million or more rose 21% in 2004, according to a survey released yesterday by Spectrem Group, a wealth-research firm in Chicago. It is the largest increase since 1998, according to the study, which was based on data from more than 450 qualified respondents. There now are 7.5 million millionaire households in the U.S., breaking the record set in 1999 of 7.1 million. The study excluded the value of primary residences, but included second homes and other real estate.

I read elsewhere that there are now 500,000 households over $10M.

$10M? There are not even a tenth that number of Hollywood celebs, TV personalities and pro atheletes in that net worth range. Some inherited wealth passed down to useless offspring. It pays in MA to be a Kennedy. My guess is that entrepreneurs and their associates, primarily but not exclusively in high tech make up a large percentage.