Facebook is halting a test it began earlier in 2012 to place its ads on other developers’ mobile apps and websites. “We are pausing our mobile ads test off of Facebook,” a company spokesman told various news outlets. “While the results we have seen and the feedback from partners has been positive, our focus is on scaling ads in mobile news feed before ads off of Facebook. We have learned a lot from this test that will be useful in the future.” Sources say one concern for Facebook and its would-be partners is that the social network isn’t ready to deliver ads on external websites that would produce significant value for either party. The ad network would leverage Facebook user data, an appealing proposition for those who have a vested interest in the social network’s ability to generate revenue from its booming mobile segment. Facebook’s shares fell 1.1 percent to finish Wednesday at $27.41. (AllThingsD, MarketWatch, VentureBeat)