I've been searching for a plugin that allows me to make membership 'invite-only'. I specifically want this in order to slowly roll-out memberships to trusted friends/family for comment-purposes. Kotaku.com does this quite well, and WordPress even did this when it was rolling out it's services (I believe).
Basically, a unique link/invite number or code is given to a trusted user + 1 extra code for them to give to a friend. With these codes, they are able to register to my blog in order to leave comments.
Anyone know of any plugins which sound similar?
Thanks in advance.