Liberty Media ( L) said Greg Maffei formally took the company's top job Wednesday. Liberty Chairman John Malone will step down as CEO, a transition role he assumed when ex-CEO Robert Bennett retired from the position last year. Malone will remain chairman. Liberty said last fall that Maffei, the former Oracle ( ORCL) and Microsoft ( MSFT) CFO, would become CEO. Liberty has large ownership stakes at a large swath of media companies including Rupert Murdoch's News Corp. ( NWS) and Barry Diller's IAC/InteractiveCorp ( IACI). It also controls companies including shopping network QVC and large European media interests. On Wednesday, Liberty shares were off a penny at $8.23.