the other possibility is, you can create two extra fields and store the ammount of users in them which have put this user on a buddylist/ignorelist
you have to change the member2.php to increase the number if someone is added:
disadvantage: this just works for new users which are put on the buddylist, so you have to revert alle lists to NULL and then add the lines into member2.php
but afterwards you can show the ammount to every user with no extra serverload
Another 2 cents, now you have 4