Although it's way too early for spring cleaning yet, AOL's ad business is sweeping a bunch of key execs out the door. Curt Viebranz, the head of AOL's new Platform A ad unit since September, has now left the company, only a month or so after Dave Morgan, AOL's former EVP for global advertising strategy, and Kathy Kayse, the former VP of marketing solutions for Platform A.

Viebranz, who was inherited by AOL through the Tacoda buyout, is being replaced by Linda Clarizio, president of Advertising.com, an ad network that forms a large chunk of Platform A.

Other ingredients in Platform A include behavioral networking entity Tacoda; ad management firm AdTech; and two other ad networks: Quigo, for text ads; and Third Screen Media, for mobile ads.

In commenting on Viebranz' firing today, bloggers speculated about a variety of reasons, ranging from possibility of cut throat ambition on Clarizio's part to the prospect that maybe Viebranz just wasn't up to par.

But in remarks made at today's Bear Stearns media conference, Time Warner CEO Jeff Bewkes gave some broad hints about other factors that might be at play.

Bewkes didn't comment about the staff departures, nor was he asked by anyone to do so. But he did tell investors at the conference that he isn't expecting to see much improvement all that soon in AOL's less than stellar ad sales.

"We do think [there will be] one more quarter of really flat advertising," he predicted.

AOL, though, is now trying to adopt a long-term strategy in building "advantage over our competition," said Bewkes. "We're going for the long-range position."

One of the "key objectives" in doing so, he said, is to take better advantage of Advertising.com -- the business unit previously headed by Clarizio -- in ways that "help our business."

Specifically, AOL plans to "run more content [through] Ad.com because that's higher margin," according to Bewkes.

In what might be seen as a bit of a contrast, under a strategy articulated by Viebranz late last year, "We will provide large brand customers with coordinated access to the full Platform A product suite, including the offerings of AOL, Advertising.com and Tacoda."

Advertising.com sells remnant advertising inventory through a vast network of Web sites.

Also at the conference this week, Bewkes essentially refused to rule out AOL's involvement in a possible future rescue of Yahoo from Microsoft's multibillion dollar acquisition bid.