There are few things which concern me and perhaps they can be changed:
1. At the moment, if you choose to show your collection to everyone, it's visible to everybody on the Internet. I would limit the visibility to registered members only.
2. The same with the forum - I would limit internal topics like Swap/Trade, Free Discussion, MPCC and so on only to registered members. Or maybe is it a good idea to limit the whole forum?
3. In general, there's too much private data around here, it would be nice if user profiles were visible only to registered members and not everyone on the Internet.
What do you think?