I have spend some time discussing this with a 5 year old, and with people who know my photograhic passion. To steal someone's photo work feels like robbery.. something like that. Being violated with no justifiable reason. The 5 year old said first must forgive and then take action if it happens again

The problem is if you just forgive, you effectively giving the right for someone to do something wrong 1st time around and get away with it. Lets see:
1. Steal your camera. First time round, never mind we forgive you.
2. Punch you. First time round, never mind we forgive you.
3. Slap you. First time round, never mind we forgive you.
.. You get the picture. Not very good..
Having said that, I know in my life I have many a times benefitted from people around me who forgave me when I did something wrong (kind souls). So, even if those photos "stolen" were mine I wouldn't want to drag an 18yr old's future down the drain because of a mistake. I much rather have him remember me as the guy who forgave him and explained to him blah blah.
If (and I am not affected by his/her actions, thus it is not for me to decide, just for me express my opinion on a very important and hotly debated subject), you just ignore what happen then you open the door for anyone to take others photos since nothing will happen....
Quite an issue... I hope that the above create a humane prespective of the problem and of its serious implications. A decision is for each one to make when the same thing happens to us!
-- Marios