Possible Duplicate:
If someone “stole” my Facebook App ID, what damage could they do?
From this post: If someone "stole" my Facebook App ID, what damage could they do? seems like no damage can be done if someone steal my appId and connect with it to facebook APIs and publish bad things on other people’s wall, right?
I’ve been thinking if I could be responsible in that case
In most cases App Id can be taken from javascript sources. The only thing that you should be worry about is App Secret.