There have been minor discussions in other threads regarding the @Username system. As of right now, your @Username is your login name and every social activity you do with your character is done to your account, not just that character. If you add someone as a friend, or join a guild, the other party will see your @Username in your list, no matter what character you are on. This means you cannot "hide" when you are online, joining a guild with one character means joining that guild with every character, adding a friend to every character.
There are quite a few pro's and con's that can be spoken for both sides of the issue. I have no information regarding if they will allow you to hide, go invisible or any other such things, if there is a source more informed than myself, please direct me to it. I did my best to word my poll in a way that tests your feelings and the strength of those feelings without loaded questions. Hopefully we can have a good discussion about a few key topics about @Username:
1. Is this system good or bad, and why?
2. Would it change your feelings if there is a Stealth Mode?
3. What kind of privacy options would you like to see?