and my suggestions

- pick a usergroup or user's that should be able to see and use this (pref user's as individuals). (just so moderators can see this as well)
- and you also need the ability to have what usergroup the referals are in, so you can tell if they're an active part of the community, i know you have posts.
- the join date of the referals
- and just a number in brackets showing the amount of people they've refered mark (4)
then you can click on mark and see who his refered!
i don't believe this to be to hard, just a few more sql statements.