Greg Coleman’s tenure as president of AOL’s Platform-A (NYSE: TWX) lasted less than 100 days, part of a major shake-up as new Chairman and CEO Tim Armstrong takes firm control.  AllThingsD’s Kara Swisher reports that the former Yahoo ad exec is gone along with CFO Nisha Kumar. Coleman’s replacement is Armstrong’s fellow Google sales alum Jeff Levick, Swisher added, citing unidentified sources. Levick’s most recent title at the search giant was VP, Industry Development & Marketing, The Americas.

—Some said it wouldn’t last:  Coleman’s ouster comes just three weeks after Armstrong replaced Randy Falco. Coleman was the third president of Platform-A in little more than a year. An e-mail to Coleman bounced back and calls to AOL representatives were not immediately returned. During an interview the day his hiring was announced, Armstrong told paidContent: “I’m actually friends with Greg and know Greg really well, so looking forward to working with him.” But several online ad industry execs I spoke with thought that the match between Coleman and Armstrong was like “oil and water.” Though both had a strong history going back to print-media ad sales, Coleman still was “an old media guy” compared to Armstrong. Also, many said the two had strong personalities and predicted it would only be a matter of time before they clashed and Armstrong would bring in someone more in line with his prescriptions for fixing AOL.

Lots more after the jump.

—More rebuilding at Platform-A?: Coleman quickly moved to put his stamp on Platform-A and continued with his plans to shuffle the deck even after Armstrong’s hiring. One of his biggest moves last month was promoting AOL vet Mark Ellis to the expanded role of EVP of sales. Ellis served as Coleman’s main advisor at Platform-A; his status now is uncertain as is that of the unit. A number of past and former AOL staffers have lamented the constant state of turmoil at Platform-A. In marked contrast, the MediaGlow programming unit under Bill Wilson has operated with a great deal more stability and has even been staffing up recently.

—A tough job to keep: Former Tacoda CEO Curt Viebranz was the first president of Platform-A, which was formed in September 2007 to house all the ad companies that AOL had acquired over the previous three years. About six months later, he was gone after disagreeing with Falco about the integration. Nine-year AOL veteran Lynda Clarizio succeeded him in March 2008. Clarizio was highly regarded for managing the Advertising.com acquisition in June 2004, and also drew praise from executives for her work on Platform-A’s integration. But the serious declines in the company’s display advertising earlier this year led AOL execs to believe they needed someone with greater sales acumen. That led to the quick hiring of Coleman by Falco. Barely two weeks later Falco and AOL COO Ron Grant were ousted themselves and replaced by Armstrong.

—Do more with less: Back to Levick, who has been with Google (NSDQ: GOOG) since 2001 and spent his first three years there as head of the financial-services group. Levick, who began his career as an attorney (just like Clarizio), started the second of his three jobs at Google in the role of Vertical Markets Director, EMEA, in January 2005. Just last week, Fortune magazine profiled Levick as one of eight “executive innovators” for driving Google’s Do More With Less program, which is designed to “educate” marketers about the benefits of measurement and accountability during a downturn.

• Start The Clock: AOL’s Armstrong Outlines His First 100 Days
• Platform-A Reorg Phase Two: Exec Shuffles, Some Teams Disbanded; Coleman Memo
• Reorg At AOL’s Platform-A; Coleman’s Turn To Clean House; Two Ad Sales Execs Are Shuffled
• AOL React: Armstrong And Coleman? Or Oil And Water; Pali’s Greenfield: ‘Tyranny Ends’
• Industry Moves: Clarizio Out At Platform-A; Ex-Yahoo Exec Coleman Brought In As Replacement