According to mobile video ad network Rhythm NewMedia, tablet ads are more inviting than those on mobile phones. In the its fourth-quarter report, the company said full-page display ads on tablets had a 21% engagement rate compared to 9.4% for the same ad units on smartphones. Furthermore, the Rhythm NewMedia report showed that combining video with full-page ads increased engagement on mobile devices from 9.4% to 11.5%.

CEO of LinkedIn Jeff Weiner has announced the sites intention of incorporating ads into its mobile display. In an announcement made on Thursday, Weiner stated that mobile access represents a large share of time users spend on LinkedIn, and said the company would start thinking of ways to monetize those page views. "We’re going to start to run some tests with regard to advertising some of our marketing solutions within the mobile environment," Weiner said.

Facebook’s IPO filing has diverted attention to its lack of mobile advertising, despite the social network boasting a mobile audience of 425 million, which is almost half its total user base. Facebook will now scramble to launch its mobile ad business before going public this spring, while Twitter could find itself in a similar situation if it decides to go public a year from now.

GroupM announced today the launch of Xaxis, a global audience buying company that combines all of the demand-side data and technology resources of WPP (NASDAQ:WPPGY) and the trading leverage of the GroupM agencies into a single comprehensive resource.