Marissa Mayer Yahoo! CEONot since 2005 has Yahoo! done this much shopping in a one year period and CEO Marissa Mayer smashed that record 5 acquisitions ago. And truth be told there is no sign of a shopping spree slowdown. It was, however, acquisition #9 this year that was the most talked about.

List of mergers and acquisitions by Yahoo!Bringing the microblogging site, Tumblr, into the Yahoo! family was no small task and came at a hefty price tag. The Tumblr acquisition, Mayer’s biggest acquisition so far, was worth a reported $1.1 billion. While the company will largely go unshaken by the acquisition it seems Mayer’s hope was to get Yahoo! playing in the arena with the big boys–Twitter and Facebook mainly. And Yahoo! is likely to continue strategic purchases as it seeks to revamp its online products and boost Web traffic.

Yahoo!, which has some 11,000 employees, has acquired more than a dozen small Internet start-ups in the past year (17 at the time of posting), focusing particularly on adding technology and services designed for smartphones and tablets.

The former Google executive joined Yahoo! just a little more than 300 days ago–at the time of the Tumblr acquisition. She currently has the second-longest tenure as CEO, first was Carol Bartz, following founder Jerry Yang’s departure from the role in 2009. If you look at the stock price of Yahoo!, in just the first 300 days, Mayer’s leadership has helped the company right its finances, bringing it up to levels not seen in years. In several days Mayer will celebrate her one year anniversary with the company and her first time as CEO of any company.Yahoo! CEOs

Investors and Yahoo! appear happy with Mayer’s performance so far and her first 300 days boast results better than some Presidents, and she has certainly taken some risks. Will these pay off? If they do, it will be have a huge impact on a company many long-thought was dead.

Since July of last year when she became the first pregnant chief executive Yahoo! may have ever had, she’s been closely scrutinized for everything from banning work-from-home arrangements at the Internet giant to reportedly setting up a nursery for her own baby next to her office and refusing to call herself a feminist. Meanwhile, she’s gotten cheers for extending parental leave for Yahoo! employees.

So, as we approach her one year anniversay let’s take a moment to acknowledge Mayer had no small task before her when she stepped into a very murky role as Yahoo! CEO and give her praise for managing to stay ahead and stay afloat. And if things keep going in this direction for Yahoo! we will likely see Marissa Mayer on day 967 of her leadership.