I came across the vS-Invites System a few days ago and I was wondering what you guys thought of the concept.

Have you been a member of a a forum that used it or something similar?

Have you used it or something similar on one of your forums?

Here's an abbreviated version of their sales pitch:
Looking to expand your vBulletin community? Invites System is an ultimate expansion for your vBulletin 3.5.x-3.8.x board that features an interface for your members to easily send our registration invitations to their friends.

  • Configurable invite expiration period.
  • History of issued invites, with color highlights and options to purge pending, expired or rejected invites.
  • Daily invite reminders and expiration notifications, can be turned off if desired.
  • Ability to define how often reminders can be sent.
  • Ability to reject received invitations.
  • Ability to permanently opt out of receiving future invitations, with automatic marking of invite as rejected and with an admincp database management interface.
  • Automatic prevention of invites from being sent out to already registered e-mails.
  • Automatic prevention of invites from being sent out to the same e-mail multiple times.
  • If applicable based on user's permissions, an "Issue New Invite" prompt is displayed in usercp for that user.
  • When an invitee signs up, invite issuer is automatically set as a referrer for the invitee, and there is no way to go around that.
  • When an invitee signs up, invite issuer and the invitee are automatically set up as buddies. Can be turned off from vBulletin Options -> Invites System
  • When an invitee signs up, the invitee can be automatically put directly into a special usergroup, if such specified in the issuer's usergroup settings.
  • Human verification to prevent multiple submissions.
What do you think? Could something like this really help to grow a forum community?