Within a few weeks, I expect to have gotten the Related Questions feature up to a standard where it makes sense to start using it a lot.
Even if I were the *only* one using it extensively, I'd expect to generate very large numbers of questions. (For two frames of reference, imagine if every answer to the Open Problems in Human Rationality had been a related question. For another, see Ruby's Space Colonization: What can we do and how do we know? post (which has 8 related questions)
The currently planned tools will let people set whether each related question appears on the home page or not (but, to have all related questions appear in recent discussion).
I feel sorta differently-worried about each way to turn this knob. Either related questions won't get enough visibility for people to actually see the ones that are interesting to them, or it'll get so much visibility that it'll drown out the site. The "optionally make related questions on home page" helps somewhat, but still leaves me with a sense that a lot of related questions will end up not getting seen by people most inclined to answer them.