Mayer said Yahoo will work with Tumblr to create ads that "are tasteful and seamless." The company expects Tumblr to start increasing Yahoo's revenue next year.
Mayer is betting that Tumblr will provide Yahoo with a captivating hook to reel in more traffic and advertisers on smartphones and tablet computers. That rapidly growing market is expected to become even more important during the next decade as people increasingly consume digital content on mobile devices instead of laptop and desktop machines.
More than half of Tumblr's users connect to the service through the mobile app, and engage in an average of seven sessions per day.
"I would characterize Tumblr as being ahead of Yahoo in terms of its work on mobile," Mayer said.
Besides offering one of the top mobile apps, Tumblr also runs one of the world's busiest websites, featuring 75 million daily posts about everything from politics to pets. Advertising has been a missing ingredient so far as Tumblr, like many online services in their early stages, focused on building a loyal audience before turning its attention to making money.
The deal also has some symbolic significance for Yahoo, an 18-year-old company that had spent much of the past decade aimlessly drifting under different management teams while Google Inc. overtook it in terms of size and influence. At the same time, newcomers such as Facebook Inc. and Twitter began to command the attention of people who found themselves spending less and less time on Yahoo.
Part of Yahoo's problems stemmed from missed chances to improve its service and technology.
Yahoo flirted with potential acquisitions of Google and Facebook in those two companies' early days, only to have the talks unravel because Yahoo wasn't prepared to pay asking prices that were far below the current market values of Google ($300 billion) and Facebook ($63 billion). Yahoo also considered buying YouTube in 2006, only to be outbid by Google, which snapped up the world's leading online service for $1.76 billion -- a price that now looks like a bargain.
Even when Yahoo did pull off deals, the company has been criticized for mismanaging a list of acquired services that includes photo-sharing Flickr, online help-wanted service HotJobs and content-sharing service Del.icio.us. Yahoo ended up selling HotJobs and Del.icio.us, but Mayer has been looking at ways to spruce up Flickr and blend its photos into more of Yahoo's other services. Mayer is expected to discuss more changes for Flickr at an event in New York Monday evening.
Tumblr could help Yahoo recapture some of its cachet with teens and adults in their early 20s, a demographic that has become tougher for Yahoo to reach in recent years as it fell behind the technological curve and struggled to develop compelling services.
While Facebook has turned into a mainstream social network where even grandparents now connect family and friends, Tumblr has become one of the places where the cool kids hang out.
"Tumblr is redefining creative expression online," Mayer said. "On many levels, Tumblr and Yahoo couldn't be more different, but, at the same time, they couldn't be more complementary."
Tumblr emerged as a trendy online hangout by providing a service that makes it easy to share blog posts, photos, video and other content in an enthralling mosaic. The service says it has amassed more than 50 billion posts from 108 million blogs. Tumblr users rely on a dashboard to pinpoint the kinds of blogs that they want to track and also have tools to pass along the posts that interest them.
That wealth of content could be interwoven into Yahoo's other services that provide coverage of general news, sports, finance and entertainment. Tumblr also will fill Yahoo's gaping void in the realm of social media. Yahoo so far has had to connect its services to Facebook and Twitter to give its users a social networking outlet.
Having its own social networking service will also give Yahoo more insights into the things that people like -- a key to distributing ads to consumers most likely to be interested in a specific products. That data, in turn, should help Yahoo sell more ads and accelerate its revenue growth. After three successive years of declines, Yahoo's revenue rose slightly last year, but lagged far behind the growth at Google and Facebook. Mayer has vowed to bring Yahoo's revenue growth back to at least the level of the overall Internet ad market.
Yahoo's acquisition will deliver a jackpot to Karp, who dropped out of high school to concentrate on computer programming. He ended up being home schooled while taking classes in Japanese and working on gambling software. Later, he became a product executive at a parenting website called UrbanBaby. After CNet bought the site in 2006, Karp set up his own a development service called "Davidville" before deciding to create an outlet for personal expression -- an endeavor that hatched Tumblr.
Karp's cut from the Yahoo deal is about $275 million. Most of the rest of the money will be paid to the venture capitalists that invested about $125 million into Tumblr. That list includes Spark Capital, Sequoia Capital, Greylock Partners, Union Square Ventures and Insight Venture Partners.