However: I think that the reviewer-to-reader ratio is tiny, and this is masked a bit by Amazon's absurd popularity.
And, to make matters worse, this absurd popularity is one of the driving motivators (cf above, "share one's opinion with the world", not "share one's opinion with the 200 people who happen to follow my micro-site.")
If anyone knows any way out of this besides increasing the number of users by several orders of magnitude, I'd love to hear it-- I, too, have a site that allows reviews, and only a tiny handful of reviewers (so far.)