I reference this article constantly at Untappd.

When we were building the NextGlass app, I took much of this into consideration for giving wine and beer recommendations.

We recently ran the query on the Untappd database of 500 million checkins and it yielded some interesting results. The "whales" (rare beers) bubbled to the top. I assume this is because users who have to trade and hunt down rare beers are less likely to rate them lower. The movie industry doesn't have to worry about users rating "rare movies", but I would think Amazon might have the same issue with rare products.