The annual Forbes 400 ranking of the richest Americans is out, and Warren Buffett is keeping his number two slot with an estimated net worth of $52 billion, $7 billion behind Microsoft's Bill Gates with $59 billion.

In a brief profile, the magazine calls Buffett the "nation's most beloved investor" and points out that he is "$6 billion richer this year despite handing over $2.1 billion in Berkshire Hathaway stock to charity in July."

This year, to make the Forbes 400 list you'd need at least $1.3 billion, $300 million more than last year.  (Not a serious impediment to Buffett, of course.)

Remember, the Forbes 400 is Americans only.  The magazine does another annual list of the world's billionnaires.  Right now, Buffett is still #2 on that ranking, but when the new version comes out in the spring look for the ongoing Carlos Slim-Bill Gates battle to push Buffett down to number three.

Questions?  Comments?  Email me at buffettwatch@cnbc.com