Yahoo has officially announced that it will acquire Tumblr in a $1.1 billion cash deal expected to close in the second half of the year, and will keep Tumblr's David Karp on as CEO. "Per the agreement and our promise not to screw it up," Yahoo says in its press release, "Tumblr will be independently operated as a separate business." In one of its first acts of business, Yahoo has moved its official blog to yahoo.tumblr.com.

"Tumblr is redefining creative expression online," Yahoo CEO Marissa Mayer said in the announcement. "On many levels, Tumblr and Yahoo couldn't be more different, but, at the same time, they couldn't be more complimentary. Yahoo is the internet's original media network. Tumblr is the internet's fastest-growing media frenzy." In a blog post discussing the change, Mayer insisted that Yahoo won't "screw up" Tumblr, and that it will operate independently. "The product roadmap, their team, their wit and irreverence will all remain the same," Mayer wrote.

Yahoo estimates that the deal will grow its audience by 50 percent, and its overall traffic by 20 percent. The company plans to infuse Tumblr with its personalization and search technology, and to fold Tumblr's massive collection of blogs into its own network. "We think there's a very compelling search story inside Tumblr," Mayer said to investors today on a conference call. "We think that there is an opportunity to grow our search business through integration with Tumblr."

And, of course, the companies will work together on "seamless" advertising opportunities. In today's call regarding the acquisition, Mayer noted that new ads may appear in Tumblr's dashboard, saying "we feel we can monetize in ways that are meaningful and add to user experience" — though she said that any dashboard ads would be "light."

Tumblr CEO David Karp also expressed a "stand pat" attitude, saying that the company will largely remain the same under Yahoo's ownership. "We're elated to have the support of Yahoo and their team who share our dream to make the internet the ultimate creative canvas," Karp said. "Tumblr gets better faster with more resources to draw from." In his own blog post announcing the deal, Karp writes that "we're not turning purple," and that "simply, Tumblr gets better faster."

The announcement follows days of speculation that culminated in Yahoo's board reportedly approving the deal on Sunday. While various initial reactions to the rumors suggested public skepticism of Yahoo's ability to improve Tumblr, some are optimistic about the deal. Speaking to the BBC, Wikipedia's Jimmy Wales said "one of the interesting things about Yahoo is that it's traditionally been viewed in the industry... as a very marketing led organization — not a great place for technologists." But Wales had positive things to say about Yahoo's new leadership, saying that "I think they have a good chance for the first time to integrate the talent from these acquisitions and actually not screw it all up. People in the industry respect Marissa as a technologist and that's a big shift for Yahoo."

The $1.1 billion buyout is considered a benefit for both parties, with Yahoo receiving Tumblr's huge community of young users, and Tumblr's investors reaping a sizable pile of cash.