Yahoo! announced it has appointed Marissa Mayer (photo ©Mrgadget3000) as new CEO of the company but also its President and member of the Board of Directors.

Two months after the resignation of former CEO Scott Thompson following the discovery that his resume was “enriched”, Yahoo! has chosen a woman who is young but already has great experience. Marissa Mayer is in fact only 37 years old but first of all she earned a real bachelor of science in symbolic systems and a master of science in computer science at Stanford specializing in artificial intelligence.

Marissa Mayer made a lot of experience working for Google, where she was the first female engineer hired in 1999, when the company was a rising star. In what is now one of the most important companies in technology, Mayer has become over time a top manager dealing with products such as Google Search, Gmail, Google News and Google Images.

From 2008 to 2011, Marissa Mayer has been named in the list of 50 Most Powerful Women in Business by the magazine Fortune and in 2008 and she the youngest woman on the list. In 2009, Glamour Magazine named her among the Women of the Year.

Marissa Mayer’s skills are indisputable, the big problem is figuring out what she can do in a company that’s declinining which for one reason or another in recent years has changed too many CEOs. This year there have been several cuts, including the lay-off of about 2,000 employees, now it might be time to start with the development.

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In her first statement, Marissa Mayer has indeed spoken of the need to bring innovative products, content, and personalized experiences to users and advertisers all around the world. In fact, Yahoo!’s press release highlites the fact that Mayer’s appointment marks a renewed focus on innovation.

Meanwhile, however, her welcome isn’t the best because Yahoo! has just suffered the theft of about 450,000 passwords from its Contributor Network, the new version of its old Associated Content. The vulnerability that allowed the access seems to have been solved and the users who registered before May 2010 – who are the ones affected – will have to follow a security procedure to change their access credentials.

Bringing Yahoo! back if not to its peak at least to being a company that matters is a very difficult job but if there’s a person who can do it probably that’s Marissa Mayer.