"This is an important investment and it's very strategic," Sandberg said of the business, which includes the company's Atlas ad server, LiveRail video SSP, and Audience Network mobile ad network. "We are going to put the time in to make this work, rather than look for any short-term return."
And later, fielding a question on Atlas adoption by agencies and marketers, she said, "This is an enterprise sale. We have to work client by client. They have to then choose us and then we have to migrate their system."
For all of its growth, both from an audience and revenue standpoint, Facebook's mobile business looks to have considerable future upside. The channel's 76% share of Facebook's business in Q2 was up 3 percentage points sequentially, from 73% in Q1 2015, and up 14 percentage points YoY, from 62% in Q2 2014.