If your application is failing with a ClassNotFoundException of the class com.google.android.maps.MapView, then the uses-library tag might be misplaced or missing from the application manifest XML.
When adding Google Maps to your Android application, make sure that the <uses -library>-tag is inside the <application>-tag of the manifest XML. This might be obvious, but I got this wrong and it took me a long time to figure out the real reason for the error.
<uses -library android:name="com.google.android.maps" />