I am very sorry, you see my intention so negatively. But I think you misunderstood my request. I am not trying to put this up secretely. The user will be aware that the favorite pictures can be seen by anyone. We also have a personal profile gallery (a phpbb mod). It is displayed right on the person' s profile and our users know it. They like to look into each other' s galleries to check for updates.
Your arguments made me wonder about this feature and revealed a problem, I have not taken care of. It is the fact, that some users already have favorite pics in their gallery. Putting up this feature would reveal those. Therefore we need to contact them and telling them to save those pictures, because they will be deleted before adding this feature.
I was always thinking that it should be obvious to our members, that their profile gallery can be viewed by every registered member. And because most of our members like to present themself in their gallery, I believe I am right on this one. This made me think the same of the favorite pictures gallery. I was wrong about that one, but I think by telling our members that this feature will be introduced and by adding explainatory text to this feature, everything should be clear again.
I came across this feature, because another community in my town has this feature, too. The community has been around much longer than our homepage. They only allow adding public gallery pictures to the users' public personal galleries. Their users are not able to upload pictures. On our community it is the opposite around. Users are able to upload pictures, but not able to present their favorite pictures of the public gallery to other users. Therefore they often save public photos to their computer and uploaded them to their profile gallery. The new feature should make things easier for them.
I hope that you can understand me a little bit better now. I do not intend to violate our user' s privacy. Thanks for giving me some hints although you do not like what I am trying to do.