Recent research have shown that the admob sdk doesn't work on Android with Eclipse by displaying the com.google.ads.adView failed to instanstiate error. Fortunately this error doesn't affect the running of the code and the code often runs on the emulator.
Searching through google shows many unanswered thread relating to this thread. It is shocking why admob will allow users go through the lengthy procedure of learning how there product works when the end result is frustrating without highlighting this bug in there product.