Well it's official: Yahoo acquired Tumblr in a cash-only deal that was finalized this weekend for a whopping $1.1 billion. The news came after several days of rumors, and as frantic anti-Yahoo pledges began appearing on Tumblr blogs. “This is ours, and Yahoo cannot take it” and “Don't let the Yahoo nightmare come true!” were common messages reblogged by Tumblr users this past week.

After the news became public this morning, users have taken on a more somber attitude of defeat: “Tumblr will never be the same”, “So long to the Tumblr was we know it. It’s been real.” Many users are also threatening to immediately switch their blogs over to WordPress.

But what will the acquisition actually mean when it comes to user experience?

In a statement by Yahoo this morning, the company makes it very clear: “Per the agreement and our promise not to screw it up, Tumblr will be independently operated as a separate business.” 26-year old Tumblr CEO David Karp adds: “Our team isn't changing. Our roadmap isn't changing. And our mission — to empower creators to make their best work and get it in front of the audience they deserve — certainly isn't changing. But we're elated to have the support of Yahoo! and their team who share our dream to make the Internet the ultimate creative canvas. Tumblr gets better faster with more resources to draw from.”

For Yahoo CEO Marissa Mayer, this is certainly a bold move. With that $1.1 billion, she wants to also buy Tumblr's audience (tens of millions of monthly unique visitors), its relatively young demographic (54% are under age 34), as well as Tumblr's “social and mobile expertise” (over 100 million active blogs). So they can't risk revamping the entire platform and potentially losing loyal Tumblr users who would abandon the site en masse.

At least they can't make huge changes right away. Tumblr currently only brings in $13 million per year in revenue, so at some point Yahoo will need to slowly integrate its ad network onto Tumblr's traditionally clutter-free interface.

It's definitely a risky move for Yahoo, but do you think it will pay off?