I bent over backwards to avoid putting the term “mobile ad network” in the headline, because Facebook is saying very little about what it is actually testing. It tells TechCrunch and confirmed to AdExchanger that it is testing selling IAB-format ads through exchanges who buy inventory from mobile ad networks. It may or may not be working directly with mobile networks also. It is anonymizing its user data, but using that for targeting – presumably for batches of similar users rather than anything 1:1. (1:1 targeting doesn’t scale cost-effectively for almost anything other than high-end financial services and medical products.) Neither will Facebook say which advertisers it is working with, though it sounds like it’s flogging mobile apps. Facebook has done some ad targeting on Zynga, and it is hungry for app discovery services it can sell to third-party app developers, who are some of its biggest web advertisers. We all expect a Facebook ad network some day, though it would be easier to build a Like-based one for the web before going mobile.