We're trying to determine if LCDS can be used as a messaging framework that will support "Internet scale" growth. All of the documentation (official and anecdotal) about number of users for an LCDS installation are in the tens of thousands at most, even when clustered. We're looking at needing to support a couple of millions of users.
Can it be done? Should it be done? Is LCDS usable outside of the corporate Intranet?
I just found this posting and thought it may answer your questions. I haven't read nor do I have any other helpful information for you but I am interested in what you discover.