YAHOO=Yet Another Hiring Over and Out (Hadley Heads Back to Microsoft)

One of Yahoo’s top marketing execs, Eric Hadley, who came to the company with a lot of acclaim in only November, is set to leave for a new job working in branding and global marketing for Microsoft’s MSN online service, several sources said.

Hadley had previously worked at Microsoft (MSFT) as GM of global advertising solutions and marketing support at MSN, although he had come to Yahoo (YHOO) from a job at Heavy.com as its chief marketing officer.

At Yahoo, he was hired as its VP of U.S. field marketing. In a statement at the time of his hire, Yahoo’s marketing and customer care SVP, Nick Besbeas, said it was a “a newly created role responsible for marketing communications strategy and execution for advertisers, publishers, industry groups and other partners.”

It’s yet another sign of renewed executive unrest at Yahoo, which continues in the wake of the hiring of new CEO Carol Bartz. Yesterday, BoomTown reported that Zimbra founder Satish Dharmaraj was leaving Yahoo, which was confirmed by the company later in the day.

Hadley seemed excited by the new role at Yahoo only a few short months ago. In his statement then, he said: “I’ve always admired the Yahoo! brand, the spirit of innovation and results Yahoo! provides for advertisers. I am very excited to be joining this great team and look forward to helping take the company to the next level.”

Well, maybe not the next level, which Yahoo is trying to reach under Bartz.

The departure of both execs is not likely related directly to her arrival, as sources at Yahoo said that the hard-charging new CEO had not yet met with all its top execs to assess the bench strength at Yahoo, or brought in any new execs save her own longtime administrative assistant.

So far, many of the troops at Yahoo seem jazzed by Bartz’s arrival as it signals change and she is known for making decisions quickly.

But the uncertainty of a new CEO and continued talks with Microsoft and Time Warner (TWX) unit AOL about various partnerships have continued to jar many at Yahoo too.