Softie Ad Exec Siebrecht to Join AdReady Start-Up

Apparently, not everyone leaves Yahoo (YHOO) to join Microsoft.

On Friday, sources said, it was announced internally at Microsoft (MSFT) that Karl Siebrecht (pictured here), the former president of Atlas at aQuantive, is joining AdReady at the end of the month as president and COO.

AdReady, based in Seattle, bills itself as an “advertising technology company focused on making online display advertising accessible and effective for advertisers of all sizes.”

The start-up has raised a total of $12 million in venture funding from Bain Capital Ventures, Khosla Ventures and Madrona Venture Group.

Aaron Finn is its current CEO and president, but is apparently giving up one title to Siebrecht.

And–probably no coincidence–aQuantive’s former CEO is Brian McAndrews, who is now managing director at Madrona.

But, sources said, Siebrecht was introduced to Finn through David Rosenblatt, an advisory board member of AdReady–and who competed with Siebrecht as CEO of DoubleClick, which was bought by Google (GOOG).

Also interestingly, Jason Kilar, CEO of premium video site Hulu, is on AdReady’s board.

Oh, it is a small tech world, after all.

Microsoft bought aQuantive–which is now called Microsoft Advertising–in mid-2007 for $6 billion and Atlas was one of its units.