Power is highly mutable. Take the world's two richest men, a couple of bridge-playing buddies named Bill and Warren.

They've been immensely wealthy for years, sure. But now, by combining their fortunes in a single philanthropic organization, they, along with Bill's wife, Melinda, just might wipe out deadly infectious diseases.

In part because of the ever-shifting value of influence in the business world, this year we decided to eliminate rankings from our annual study of the subject and instead provide, literally, snapshots of power: In the gallery that follows are 25 portraits, photographed by Albert Watson, of the characters who had the most impact on 2006. »»»