I disagree I think it is the biggest issue we face. If anyone can solve this problem, it would make the site 1000x better instantly.I am aware that this is not exactly a major issue, as Hubski is currently working out fairly well, but i feel it would make for a larger range of opinions to be displayed did more people feel willing to add to the experience.
If people aren't by nature the types to comment or post, then there is no use trying to change that. If only a small percentage of people comment/post, then we don't need to change those that aren't comfortable doing so, we just need more people. I think Hubski with about 100k people would be awesome. It could still feel small and would allow for a ton more discovery. But as for user behavior, you can't fit a square in a circle, not worth trying.