I have Problems with Prime31 SocialNetworking Plugin because the Unity Main Activity will be overwritten by Vuforia.
Here are two discussions on the subject:
http://prime31.com/support/5659/social-networking-v3-0-1-with-vuforia-problems
http://prime31.com/support/5428/socialnetworking-android-another-prime31-overrides-activities
What can you do with such a problem? Or must I live with this problem that some plugins are not compatible with Vuforia? Is a better solution planned in the future?
The next Vuforia release should address this aspect of the Unity integration; though, I do not have any dates to share for such release at this time.