There's this teeny-tiny little interactive tool called myspace that allows can be set up to be only accessed by your "groupmates".
And there are many, many other places to set up private "interactive areas". Going into a public forum and saying "don't post here", is about as realistic as going into Times Square and telling everybody to shut up because you want to have a private conversation.
Oh, and why create a new username?
Anyway, more muppet goodness: