Facebook’s mobile advertising business accounted for almost a quarter of sales at the social networking giant last quarter, prompting founder Mark Zuckerberg to declare that the firm had finally become “a mobile company.”

Mobile revenue accounted for 23 percent of advertising revenue in Q4, up from 14 percent the previous quarter. The return is further proof that Facebook is beginning to find ways to monetise its mobile presence, healing a rift with those investors that had accused the firm last year of lacking a coherent mobile strategy.

“Facebook Q4 2012 results give cause for optimism and suggest the company is on the right track following its disappointing IPO and the lacklustre two quarters that immediately followed,” said Ovum analyst Eden Zoller.

Total Q4 revenue came in at $1.585 billion, a 40 percent increase year-on-year. Revenue from advertising was $1.33 billion, representing 84 percent of the total. But net income fell to $64 million from $302 million a year ago, on the back of rising “costs and expenses” which topped $1 billion, up 82 percent.

The number of Facebook’s monthly active users (MAUs) stood at 1.06 billion at year-end 2012, an increase of 25 percent year-over-year. Mobile MAUs accounted for 680 million, an increase of 57 percent. The number of daily active users (DAUs) was calculated at 618 million, with the firm claiming that mobile DAUs exceeded web-based DAUs for the first time in Q4.

“In 2012, we connected over a billion people and became a mobile company,” declared Zuckerberg.