On vbulletin we have a function that shows the staff which member has read a thread and at what time. In case of abuse this is very handy and allows us to catch malicious users like multiple accounts. Its also useful for staff to see if users have read a staff post. There also used to be a popular addon that allows you to track a users behavior on the site. This is useful if the staff thinks there is a malicious user active and they want to monitor and track its behavior. It would be useful if such addon would be available. I would surely buy several licenses.