Calvin Klein, Twentieth Century Fox and Turner Broadcasting are a few of the launch brands that are testing a new mobile ad format from Tumblr that inserts a piece of ad content within popular and trending posts.

As more social media usage takes place via mobile, Tumblr wants to follow in Twitter and Facebook?s footsteps and cash in on brands looking to promote their content through native ads that appear as a piece of content. Despite the opportunities with native ads, Tumblr faces challenges around content regulations and guaranteeing that the ads are not seen as obtrusive.

?Tumblr delivers a much more concentrated younger audience than Twitter or Facebook where younger audiences have eroded recently,? said Jesse Cahill, client director at Essence, New York.

?If brands are interested in connecting with audiences under 25, Tumblr or Reddit are the best social networks to tap into, not Facebook or Twitter,? he said.

?This unit should absolutely help Tumblr monetize more effectively on mobile, as appearing next to more premium trending content should help them command higher rates and address some of the concerns around brand safety that occur when advertising in a user's Tumblr stream itself.?

Mobile engagement
This is the second mobile and fifth digital ad offering that Tumblr has rolled out this year as the company looks to monetize its services after being acquired by Yahoo in May for $1.1 billion.

Earlier this year, Tumblr rolled out a sponsored mobile post ad that places ads within a news feed.

The new sponsored mobile posts pop up in the Explore tab within the trending blogs section in Tumblr?s apps for iPhone, Android and Windows Phone devices.

Trending blogs is a section that curates content based on traffic and increases in followers.

The ad unit stretches across the screen and resembles a normal piece of content. A money sign in the top right-hand corner of the ad indicates that the post is sponsored.

There is also a Web sponsored post ad unit that shows up on Tumblr?s Web site.

As more social media access moves towards mobile, all of the big social networks are battling for brand spend to monetize services while also retaining the user experience.

Twitter recently revealed in its initial public offering that 75 percent of its revenue comes from mobile. 

Additionally, Twitter is aiming to make a bigger name for itself in driving commerce for retailers with brands including Starbucks leading the charge (see story).

Facebook?s efforts to date with mobile have also been successful with 40 percent of revenue coming from the medium.

Tumblr?s inherent focus on snack-sized content sets it up well for mobile. 

"The magic combination in social media marketing is when content marketing, social promotion and closed-loop analytics are applied," said Marko Mueliner, senior director of marketing at ShopIgniter, Portland, OR.

"Tumblr has the technology and ad units to bring this recipe to brand advertisers in a meaningful way," he said. "The test will be to see how they implement these elements to drive social performance marketing, that is, business-impacting campaigns that can be measured against marketing goals and objectives."

However, both Facebook and Twitter offer mobile advertising units that are more targeted to specific groups of consumers.

For example, Facebook recently launched an app retargeting unit that lets marketers serve tailored ads with specific content to consumers who have already downloaded a mobile app (see story). 

There are also some safety concerns about the type of explicit content that Tumblr is notorious for. Since its Yahoo acquisition earlier this year, Tumblr has slightly tightened its content restrictions so that it is harder for consumers to find adult content.

Tumblr's its reputation could still hold back marketers from fully embracing the social site as a marketing channel.

Similar to other news feed-based ads on Instagram, Facebook and Twitter, there are also Tumblr users that are upset with seeing ads mixed in with content that they follow.

?Having a competitive ad product will definitely help Tumblr steal some ad dollars from Facebook and Twitter, at least in the near term,? said Dave Martin, senior vice president of media at Ignited, El Segundo, CA.

?But what remains to be seen is how well these ads help brands achieve their marketing goals,? he said. ?There is already a lot of backlash from Tumblr users about new content restrictions and the presence of ads in the newsfeed. If users start to migrate off of the platform, you can expect early advertisers to march right back to the bigger platforms.?

On-board brands
Twentieth Century Fox was the first brand to launch a mobile trending blogs campaign. 

The film studio is leveraging the native ad format to promote the upcoming film ?Devil?s Due,? which premiers in theaters on Jan. 17. When consumers click on the ad, they are directed to a Tumblr that has been created for the movie.

Twentieth Century Fox will also run a campaign to promote its film "Secret Life of Walter Mitty? in the coming weeks.

Turner Broadcasting is kicking off a campaign today to promote its series ?Mob Cities? that premiers tonight. 

Delta?s campaign to drive traffic to its Tumblr ? Taking Off ? will begin running tomorrow.

The dates for the Calvin Klein campaign are not confirmed, but the high-end retailer will run a sponsored mobile ad on three different days.

?Tumblr is a content network, a social aggregation content network,? said Craig Elimeliah, vice president and director of creative technology at Rapp, New York.

?It makes perfect sense for those marketers already getting earned placement on Tumblr blogs that are fashion-focused and lifestyle-focused,? he said.

?Tumblr shouldn't be competing with Facebook and Twitter. Tumblr in my opinion should be competing with BuzzFeed and other more mobile-optimized content networks.?