CES: Katie Couric, John Legend Accompany Marissa Mayer for Packed Yahoo Keynote

LAS VEGAS — Yahoo CEO Marissa Mayer declared mobile a key part of the Internet giant’s future and unleashed a flurry of announcements designed to help pep up the historically underperforming company’s stock price.

She also was joined onstage by Katie Couric, who discussed her new role as Yahoo’s global anchor; John Legend, who performed a trio of songs; and SNL castmembers, who performed a “Weekend Update” sketch.

“Yahoo’s core values are making the world’s daily habits inspiring and entertaining,” Mayer said. “For Yahoo and the wider industry, mobile is all about growth. By 2017 we expect 3.1 billion devices connected to the Internet, nearly 2 billion more than we see today. And it’s what people do on their mobile phones that counts.”

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Part of her plan is to refresh news. To that end, Couric noted her excitement about the “blank slate” she is starting with in her new role. “I really enjoy interviewing and look forward to interviewing tech leaders, authors … anyone who has an interesting story to tell. The global reach is exciting for potential interview subjects.”

Commenting that she started her career when ” ‘harass’ was two words instead of one,” Couric noted that that attitude today is no longer ubiquitous, “not when a programmer thinks you should get it.” She added that Yahoo will maintain the “old-fashioned values of journalism, like perspective and integrity.”

Yahoo also aims to shake up advertising with what senior vp advertising technology Scott Burke called “a new unified ad solution, which will make media-buying a lot more efficient.”

Tumblr-sponsored posts will now be powered by Yahoo Advertising; Yahoo Audience Ads will help advertisers reach users across Yahoo sites and other inventory; and a new buying platform will underpin these. A Yahoo Ad Exchange is launched for premium publishers.

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Yahoo’s media division will feature new services through the company’s own video and image services Flickr and Tumblr. Said Mayer: “We have overhauled four core media properties to bring an endless stream of curated properties to users.” These include ABC Good Morning America and NBC Sports.

Yahoo News Digest is a new app aimed at simplifying news stories and information overload for consumers. According to product manager Nick D’Aloisio it will be “algorithmically produced but editorially curated.” Information is pulled from a variety of agency sources, including AP and Reuters, and is supported by material culled from the Internet — graphics, maps, tweets, video and images.

For more in depth content, Mayer announced new consumer websites that she called digital magazines. The first two of these theme-based sites are Yahoo Food and Yahoo Tech. Instead of banner ads, Yahoo will finance the sites with ad-funded content.

The acquisition of contextual search specialist Aviate was also announced. This technology is aimed at automatically organizing apps based on contextual clues to serve users with personalized information on their mobile devices. “The future of search is contextual knowledge,” said Mayer.

The exec added that Yahoo had performed more than 600 experiments to continue innovating its search functionality and had 869 search partners.

Adam Cahan, senior vp mobile and emerging markets, said, “2014 is poised to be our biggest year in video yet” and launched a smart guide that brings together autorecognition capabilities and recommendations for live and VOD content to smart TVs.

Added Mayer: “The industry is at a critical moment, embarking on the next-generation of video consumption. Video is interactive, cross screens and programmed by the user.”

The support cast to all this included Cecily Strong from SNL, who performed a “Weekend Update” sketch with castmember Kenan Thompson as Al Sharpton, who thanked “Yoohoo,” adding: “Who thought a chocolate milk company could turn into one of the world’s top tech giants?”

Yahoo has 800 million users worldwide.