- Brian Morrissey

NEW YORK AOL has shuffled leadership at its ad network business, replacing president Curt Viebranz with Advertising.com president Lynda Clarizio.

Viebranz served as president of Platform-A, the unit AOL formed in September to house its ad network businesses. Clarizio will now run both Advertising.com, which is based in Baltimore, and Platform-A in New York.

An AOL rep declined to elaborate on Viebranz's departure, saying only that he had left the company. Viebranz referred all questions to AOL.

"Lynda Clarizio is the perfect choice to lead Platform-A to its next stage of growth, as we consolidate and integrate the organization, and focus on bringing our unmatched advertising network to market," AOL president and chief operating officer Ron Grant said in a statement.

AOL formed Platform-A to house Advertising.com, Tacoda, Lightningcast, Third Screen Media and AD TECH. Company officials have deemed it critical to AOL's future as it shifts to a full advertising model because of it potential to reaggregated audiences fragmented across the Web.

Viebranz is the latest high-ranking AOL advertising executive to depart. Dave Morgan, who was founder of Tacoda, departed departed his post as evp of global advertising strategy in February. Viebranz served as CEO of Tacoda prior to its purchase by AOL last July. Kathy Kayse, vp of marketing solutions for Platform-A, left AOL for Discovery Communications.

Clarizio joined Advertising.com in May 2006 from AOL, where she was an evp in its audience business. She has spent over a decade at AOL in several roles, following a legal career in Washington D.C.

At the time of Platform-A's formation, Viebranz, Clarizio and Kayse were its top executives.