• by Joe Mandese  @mp_joemandese, July 26, 2011

Joel Lunenfeld, one of the most knowledgeable executives on Madison Avenue about social media, is out as CEO of Publicis' Moxie unit has left to become director of global brand strategy at Twitter. Scott Neslund, a long-time Publicis media executive who joined Moxie in March as president, will lead the agency.

Lunenfeld helped found Moxie in 2001, and previously had been a media executive with 360i. He joins Twitter at a time when the micro-blogging service is literally atwitter on Madison Avenue, and is looking for ways to capitalize on rapid growth.

Neslund, who will remain president of the Atlanta-based agency, which is a division of Publicis' ZenithOptimedia Group, will also take Lunenfeld's place on ZenithOptimedia's North American Management Committee, reporting to ZenithOptimedia chief Tim Jones.

Neslund, who previously was a senior executive at Publicis' Starcom MediaVest Group, left to become CEO of WPP's Mindshare North America division, and then left Mindshare to take the dive into digital media, joining Red Bricks Interactive before joining Moxie earlier this year.