Private Messages and Link Contact to User

[Superman859]

I have a question regarding the private messaging system and the 'link to user' option for manage contacts.

First off, are the only people who can private message those who have backend access, such as administrators?

Secondly, what exactly does the 'link to user' option do when you set up a new contact?  I tried it, but I didn't see any effect other than when you go to the user manager and see the user, it has a link to that contact management for the user.  Is that all it does?