Lots of interesting and potentially useful points. But everything depends on knowing or controlling the quality of HN: Is it deteriorating? How do we increase it? Etc.

So: We need to be able to measure the quality of HN. This doesn't sound any easier -- maybe it isn't. But the process of figuring out how to measure the quality will take us a long way toward telling us how to maintain and increase it.

Without measurement, we don't really have a basis for agreement on whether a change to the mechanism is good or bad.