Warren Buffett challenges (other) billionaires re their tax rates

Warren Buffett is getting some feedback from his billionaire club colleagues to his million-dollar tax challenge, and it's not all that positive.

In an interview with NBC's Tom Brokaw that aired last week, Buffett took his "I'm not paying enough in taxes, and neither are my fellow billionaires" campaign to a new level, highlighting his contention that he pays a lower tax rate than all of his office employees.

He told Brokaw: "I'll bet a million dollars against any member of the Forbes 400 who challenges me that the average (federal tax rate including income and payroll taxes) for the Forbes 400 will be less than the average of their receptionists."

"So far only three close friends, all 400 members, have made the calculation for me. They all came up with results similar to mine but have no interest in being identified."