Facebook's (FB -1.5%) on-again/off-again efforts to launch a mobile display ad network are back on: The social networking giant says it has started a new test in which targeted Facebook ads will be shown within 3rd-party apps.
Though Facebook has done similar tests before, the company says this one is "more like a mobile ad network" in that it's working directly with publishers and advertisers, rater than a 3rd-party ad-serving platform.
Facebook's move is aimed at Google's (GOOG -0.2%) AdMob unit, the unquestioned leader in the mobile display ad space, and also Twitter's (TWTR -0.2%) recently-acquired MoPub mobile ad network/exchange unit. Millennial Media (MM -0.3%) and Apple's iAd unit also compete in this market.
Twitter reportedly plans to launch a mobile ad network that leverages both MoPub and Twitter's user data.
Helping Facebook's cause: The company has mountains of user data that it can rely on to deliver targeted ads, and its mobile ad business already works with thousands of app developers (courtesy of its app install ads).
In spite of AdMob, the growing share of Web usage claimed by mobile apps remains a threat to Google's massive share of online ad spend, given the latter is heavily tied to search activity done via Web browsers.