I would imagine that any kind of collecting has a similar basis - though in the case of something connected to sexuality, there will probably be an emotional investment in the collection over and above that of something like stamps, butterflies or footie stickers. But I think the word 'addiction' is bandied around too much these days - people seem to claim an addiction to pretty much anything!

I think it is appropriate here because as you pointed out there is quite a lot of emotionality involved - arousal even - and of the most potent type - our sexuality. I can only go on my own experiences and of others I have met and from the literature but I think addiction is the word to use. Not only does it appear in image collecting but also in the way we tend to fantasise I think. These fantasies tend to evolve and get more explicit as they lose their power to satisfy us - from personal experience too. Sex-addiction itself also is one aspect of pedophilia too I think. It may also be one of the reasons why some of us initially have our attraction. The following I came across recently - not new however:

http://query.nytimes.com/gst/fullpage.html?res=9B01E3DA1138F93AA25752C1A9669C8B63&sec=health&spon=&pagewanted=all

also this - not relevant but I thought you might like it - about teaching in Austria:

http://forums.abrsm.org/index.php?showtopic=23546

Moth