There's little denying the fact that relatively new Yahoo! (NASDAQ: YHOO) CEO Marissa Mayer means business. Since taking the helm just 10 months ago, she's already led Yahoo! to 10 acquisitions, has eliminated off-site work in an effort to improve productivity, and unlocked value through the partial sale of its stake in Alibaba for $7.6 billion in pre-tax profits.

The big question on everyone's mind right now is whether or not the Tumblr acquisition for $1.1 billion announced earlier this week is the game changer that Yahoo! needs. I believe the answer to this question is, "Yes, and no."

Taking the Tumblr
On paper, this is exactly what Yahoo! needs. It's fallen light years behind rival Google (GOOGL 0.55%) and has even ceded share to Microsoft's (MSFT 0.37%) Bing in terms of attracting younger viewers and in building its mobile readership. As of comScore's most recent search engine market share data from April, Google controlled 66.5% of all traffic, followed by Microsoft at 17.3% and Yahoo! at 12% (which is actually a hair lower than the last time I referenced this figure in September). Yahoo! has tried redesigning its home page before to attract viewers, but it's been relatively unsuccessful. In fact, Bing's TV ad campaign completely targets Google as its primary foe, ignoring any threat Yahoo! poses to search.

The Tumblr acquisition, though, will provide an almost immediate 50% boost to Yahoo!'s total readership which stood a bit over 700 million people prior to the purchase. Tumblr's approximately 300 million unique users per month are made up mostly of millennials and are the age group that Yahoo! sorely needs to attract to drive traffic to its site and reverse a multiyear downtrend in display ad revenue.

Will mobile ads provide the spark?
Another area where promise and peril exists for Yahoo! is in the mobile advertising space. While Google does boast the largest market share here as well, there's no set formula for success like in standard PC search (where it currently dominates). This means that smaller players like Millennial Media (NYSE: MM), which has dropped precipitously since disappointing investors with its fourth-quarter results, still have a shot at harnessing significant market share.

On the flip side, according to data from research firm IDC, mobile publishers like Facebook (META -0.52%) are taking market share rapidly from traditional publishers like Google and Millennial Media. Facebook, which didn't even have mobile revenue a year ago, reported in its latest quarter that mobile ad revenue made up 30% of the company's $1.25 billion in ad revenue. That's tremendous growth in under a year's time frame!

Is this Flickr all over again?
We've seen that Mayer has no problem with purchasing the growth that Yahoo! has been unable to attract under previous CEOs, but can Yahoo! continue to nurture growth from these acquisitions down the road, or will its omnipresence crush their growth --, just as it did with Flickr?

One of the big reasons Flickr's flame dwindled wasn't because people lost interest in Flickr -- it was because Yahoo! tried to integrate Flickr with its own business goals and took Flickr's creative team away from innovation and focused them on integration. Yahoo! has a history of acquiring companies and trying to assimilate them which just doesn't work well! In Flickr's defense, Yahoo! has revamped its home page with a fresh new look, beefed up its storage space to 1 TB, and is trying to make inroads on the globally dominant Android OS with a new app. But instead of maintaining its previously dominant status, Flickr's now having to play catch-up.

I ultimately feel that if Yahoo! can somehow leave these recent acquisitions alone while forging partnerships with mobile ad players like Millennial Media, it has a shot at success -- but I'm not holding my breath.