I encountered the same incident too, lost a $300 account. I send lots of appeals. No answers, no explanations. The incident made me wonder: "should I always depend on Admob?".
So I decide to combine several Ad networks. It works. And I realize something about Admob:
Pros: It is reliable and has huge users database. Admob is backed by Google - a prestigious corporation who tracks every steps of anyone who use its service.
- Its eCPM is low (I don't know exactly why but everytime I try another Ad network, they outperform Admob in terms of eCPM. I guess that Admob know it has advantages over competitors when it comes to reputation and users database, so It charge advertisers and publishers more)
- Its ban users more frequently & it's nearly impossible to get the explanation from them. (Some of my friends' accounts got banned because Google thinks they was cheating, while infact he didn't. It was very difficult for him to reach Google support to recover his accounts).
After combining Admob and with Airpush, Leadbolt, StartApp, ChartBoost, I end up with Adsota - a lesser known ad network. Adsota is an has much higher eCPM, 100% fill-rate, variousa ads format, and swift payment. You can find it by googling "ads.appota".
Best of luck, mate!