This is a useful thing..
And this is why..
When logging in to the forum, your username and password is stored into cookies on your pc. Theese cookies can be stolen through linking to other sites, which has the cookiegrabber on it..
Which means the grabber can now convert those cookies from a (usualy) simple encryption and from there, login to your account -> He can acces and do everything with your Forum gold.
Now.. If you use this pin code system..
This pin system is not attached to the login system.. Which means, this doesn't use cookies. You will be using this as an extra password. It will function exactly as the login password -> you will be able to change the password, or send it to your email.
So everytime you wanted to spend Forumgold, you would have to -> Go to the bank -> Widraw gold (pin required) -> Send forum gold (pin required).
Now this system could be on alot of the features on the website.. Say like.. The password change, the email change etc.
This way.. if the grabber of your cookies gets logged in, he wont be able to steal any of your forum gold or anything.