I've been working on integrating Facebook Audience Network ads. Before going "live", Facebook says that they have to approve the ad placement - they say this approval is initiated automatically when you've had 5 successful test ads and that the approval takes 2-3 business days.
In my case, I displayed some test ads on the simulator, and also on a device. They tell you to use the API and register the device with a hash code they provide.
After almost a week, I hadn't heard anything from Facebook and was wondering what was going on. After doing some online research, I found a discussion that suggested that the number of impressions was important.
I reran the app - this time with it running on a local device connected to Xcode. On each refresh, it would write [FBAudienceNetworkLog/FBAdUtility:396] Impression is logged (displayed for test ads only) to the console.
I let it go for a few minutes until there were at least five of these impressions.
Then, to my surprise, less than a minute or two later, I received a Facebook alert saying that the app had been approved.
I had a second app that I repeated the process with. Again, after just a few minutes, the app was approved for ads.
*** Update 3/28 ***
Okay, after doing a few more apps, it seems that Facebook has changed the process such that they just automatically review apps after a few days. I'm guessing that the number of impressions still matters, but it seems disassociated from when they actually review.