In theory (assuming that there are links to everyone, and no way to have separate networks) (it's of course a theory only, but seems very likely that there are "massive users", who have files of "every kind", connecting the different groups), as long as you both connect to one who is connected, it will work.

Although this is quite the extreme case, and not really the purpose for Bittorrent to begin with, I guess. The main interest is load balancing of popular downloads, not finding the one person with the one file for you.