John wants to be able to allow friends to add photos to his albums on Google+. Leo says he isn't sure if that can be done at the moment because Google is in transition at the moment.
One thing he can do is create a public folder on PicasaWeb. Unfortunately, that's going to end soon, which is too bad because Picasaweb is full of features that Google+ doesn't have.
The best option would probably be Flickr. That gives him the opportunity to create a Group which others can add to.
John could also use Google+ Events, which comes with Photo sharing.