I write a lot about how movies are rated on imdb, and I'm going to continue to because I think the way the system works is fascinating. But before I do so, I have just one bone to pick.
You might not think that rating systems are a very big deal, but they're all around you. Amazon and The New York Times have book reviews. Yelp and your local paper do restaurant reviews. The US News and World Report does a very important and influential review on colleges. IGN has extremely influential video game reviews that I use to base my video game purchases on. You could even view democratic elections as one long, lumpy, and fairly inefficient rating system.
And now that the internet is able to bring millions of people with independent opinions into one place, they're going to matter more and more.