I sell subscriptions to my site on a 1-to-1 basis.
I've been approached by an organisation who want a bulk rate for their entire organisation, but don't want their staff to have to authenticate using username and password. Rather, they want my site to be able to automatically allow access to their staff based on their office IP address (static).
I've had a quick look around the web, but haven't been able to find any extension that seems to be able to add this functionality.