Between November 2008 and March 2009, Redmond hired away five Yahoo veterans. First, Sean Suchter, VP of search technology at Yahoo, left to become general manager of Microsoft’s Silicon Valley Search Technology Center. Then Yahoo search scientist Qi Lu followed him after being tapped as president of Microsoft’s Online Services Group. Soon after that, Larry Heck, former VP of search & advertising sciences at Yahoo Labs, accepted a job in the R&D department of the software giant’s online services division. Jan Pedersen, who once served as a chief scientist and VP of Yahoo’s Search and Advertising Technology Group and Dayne Sampson, Yahoo’s VP of operations for search and advertising, followed.

Now comes word that three more Yahoo execs have taken jobs at Microsoft (MSFT). Knut Risvik, Yongdong Wang and Kevin Timmons, all Yahoo veterans, are now headed to Microsoft.

Risvik, once a chief architect at Yahoo (YHOO), will work on Microsoft’s search platform and infrastructure. Timmons, formerly a Yahoo VP of operations, has been charged with running the company’s data center expansion. What Yongdong Wang, once a VP of international search, will do remains to be seen. He is, however, reporting to Harry Shum, Microsoft’s corporate vice president for search product development, so presumably he’ll be doing something similar.

A nice little trifecta for Microsoft and one that surely inspired Yahoo CEO Carol Bartz to drop a frustrated F-bomb or three. As I said back in March: If Yahoo employee defections to Microsoft continue apace, there may come a day when Redmond will no longer need to buy the struggling company’s search business. It will already have acquired it.

“We’re very excited to have Dayne Sampson join the team, reporting to Debra Chrapaty, corporate vice president, Global Foundation Services,” a Microsoft spokesperson commented about the hire. “Operations and foundation services are key to delivering the Microsoft Software plus Services vision, and Dayne’s extensive operations and industry experience will be a strong asset for GFS and the company.”

Sampson’s departure follows similar migrations by Sean Suchter, Yahoo’s VP of search technology; Qi Lu, one of its top search scientists; Larry Heck, former VP of search & advertising sciences at Yahoo Labs; and Jan Pedersen, who was once chief scientist and VP of Yahoo’s (YHOO) Search and Advertising Technology Group. As I said last week, If Yahoo employee defections to Microsoft continue apace, there may come a day when Redmond will no longer need to buy the struggling company’s search business. It will already have acquired it.

Oh, one last thing: time to update that LinkedIn profile, Dayne…