Mobile browser developer Opera have released their quarterly State of Mobile Advertising report. Metrics and trends cover the 2nd quarter of 2012, and are based on their mobile ad platform which serves more 35B ad impressions per month. See the report here, some notes below.

· iPhone leads smartphone OS with an average eCPM of $2.85

· Rich media drives better engagement. Leveraging native functions of mobile devices (HTML, camera interfaces) has a direct correlation to time spent interacting with the ad unit. For example, 66% of users that click through to a video will complete that interaction.

· HTML5/Rich Media accounted for 51% of all ads run. Standard ad units 21%, Video 13% and Expandable Banners 15%.

· Among all publisher categories, Business & Finance generates more revenue per impression than other category.

· The U.S. and Canada generate the majority of ad requests, accounting for 73% of the global total.