Many chief executives shake up a company when they move into the top job. It's in part a need to stamp your own image on the company and also a chance to rectify past mistakes.

Carol Bartz's announcement of a shakeup in Yahoo's management structure was expected, but the speed with which she has moved will surprise some inside and outside the company.

Bartz has spent the past six weeks interviewing staff, travelling around to different locations and building her business plan. Today she put it into action.

In her first blog posting on the Yahoo Anecdotal blog Bartz promised a major shake-up, both in how the company is run and in how it presents itself.

"So today I'm rolling out a new management structure that I believe will make Yahoo a lot faster on its feet," she wrote.

"For us working at Yahoo, it means everything gets simpler. We'll be able to make speedier decisions, the notorious silos are gone, and we have a renewed focus on the customer. For you using Yahoo every day, it will better enable us to deliver products that make you say 'wow'."

We have already seen some changes. The departure of chief financial officer Blake Jorgensen had been expected for some time, despite his only joining the group in 2007. He was widely seen as being close to Sue Decker, who left shortly after Bartz took over.

The company has already announced the promotion of David Ko from the company's Asian office to head up Yahoo's mobile division, replacing Marco Boerries, who will be leaving the company.