Marissa Mayer: Some Tumblr users “may never come to Yahoo,” and that’s OK

Yahoo (s YHOO) may have acquired Tumblr for $1.1 billion, but Yahoo CEO Marissa Mayer stressed in an investor call Monday morning that Tumblr will continue to operate as a separate business — aided by Yahoo infrastructure but not hindered by the larger company. The stock market’s reaction to the deal has, so far, been tepid, with Yahoo shares settling to where they started after a brief surge at the opening bell.

“Part of our strategy here is to let Tumblr be Tumblr,” Mayer said. In fact, Tumblr CEO David Karp wasn’t on the morning’s call: He was at an all-team meeting. (“Instead of calling his all-company meetings ‘all-hands,’ he calls them ‘all-team,'”Mayer noted. “I think in the future we’ll call meetings at Yahoo ‘all-team’ meetings.”)

“When you look at the best and most-successful billion-dollar acquisitions in the tech space — eBay (s EBAY) and Paypal, Google (s GOOG) and YouTube — there’s a meme that emerges,” Mayer said. “The best acquisitions…allow the two brands and the two products and services to evolve somewhat separately.”

Yahoo has “well over” 700 million users, Mayer said, while Tumblr has 300 million — but these audiences overlap so little that the companies can count their combined user base at over a billion.

The difference in user demographics, Mayer acknowledged, means there’s “a type of user that will always prefer Tumblr and may never come to Yahoo” — and that’s fine. Yahoo can “provide search seamlessly in the background” for Tumblr, but it could be existing and future Yahoo users that benefit most from the Tumblr acquisition: “As we pull Tumblr content into our news feeds and our media experiences, it will cause the core Yahoo properties to become that much more interesting and that much richer,” leading more users to the site even if they are from “very different [demographic] profiles from people coming to Tumblr.”

Tumblr users should get ready for more ads

Tumblr will remain a separate site, but that doesn’t mean its users won’t notice a few changes — particularly on the advertising front. “There’s a number of different places where we think we can monetize in a way that’s meaningful and really additive to the user experience,” Mayer said. Tumblr is already including a few ads in its dashboard, but “we would like to look at that and understand how we can introduce ads — a very light ad load where the impact is really created because the ads fit the user’s expectation and follow the form and function of the dashboard.”

In addition, Mayer said that Yahoo might allow individual Tumblr users to enable ads on their blogs, “but that would always be done with the blogger’s permission.”

So what about Tumblr CEO Karp’s well-known dislike of advertising? “David talks wistfully about the ads that he saw as a child, that would make him want to go see a movie or own a particular type of car,” Mayer said. “He says the current state of internet advertising doesn’t aspire to be as good as the content itself. We think that should change…we’re aligned in those ideals. When you hear us talk about native ads, where the ads are every bit as good as the content, and maybe even make the content better — that’s what we are aiming for. We want the ads themselves to create that aspirational feel that, for example, television ads or movie ads do.”

So, uh, what about Flickr?

In 2005, Yahoo acquired photo-sharing service Flickr. That acquisition, long before Mayer’s time, is widely viewed as a big failure — one that ruined the Flickr experience because Yahoo tried to integrate it, then largely abandoned it.

On Monday afternoon, though, Yahoo is expected to announce updates to Flickr. Could we see a resurgence in that platform, as part of Yahoo’s new “don’t-screw-it-up” acquisition philosophy? Mayer was cautious: “In terms of how Tumblr evolves, it really depends on the creators,” she said. But when it comes to Flickr, “I think it is noteworthy that a lot of the posts on Tumblr are graphical. There’s some obvious synergies between Flickr and Tumblr, in that regard,” and it’s “probably something we’ll turn our attention to in the future. Flickr could provide great storage for albums or slideshows, things like that. We’ll see.”