If you are using Proguard and the Admob the adapter is included but the AdMob SDK is getting stripped out, then when a call is made to that ad network, an application error will occur.
In your configuration file of proguard (proguard.cfg), simply add this line:
AdMob Support
-keep class com.google.ads.**
Make sure that you also have these 2 lines for MoPub integration:
-keepclassmembers class com.mopub* { public *; }
-keep public class com.mopub*
That should prevent AdMob from being pulled out.
Please also see our Proguard documentation for Android here.
