Putin overtakes Obama in 'world's most powerful people' list

US president Barack Obama has been ousted from the number one spot in an annual ranking of the world's most powerful people by Russian counterpart Vladimir Putin.

British Prime Minister David Cameron's influence on the global stage has also diminished, as he drops out of the top 10 on Forbes magazine's list, slipping one place to 11th, behind Wal-Mart CEO Michael Duke.