In Facebook chat, to the right sidebar, when I am signed out of chat, I have a list of friends that show up greyed out.  What does this list represent?  I am consistently having two friends show up in order of one another who are not FB friends in themselves.  Is this possibly disclosing two individuals that are chatting or messaging one another?  If so, this would seem to be a big security breach and I would want to know how to keep my own user id from appearing in such a list. 
Facebook chat, friends that show up as greyed out
facebook;facebook chat