Whenever I'm on Amazon, I take great comfort in the fact that I can see a distribution of the star ratings of book reviews in a handy graph format. So, for example, if a book has 2,000 one star ratings and 5,000 five star ratings, and very few ratings in-between, I know that this is the kind of book I'll either love or hate. And if the low ratings are comprised of didactic rants about the immorality of the writer or are filled with personal vendettas, it's easy to see that as well.
It's helpful that the same star distribution system has come to Android Market. Why? Well, if an app has just been posted, and it only has a couple reviews, and most are positive but there are just a few negative reviews, it will bring the ratings average significantly down. But by posting the star distribution, users can easily see how a few low star ratings brought the average down.
Now, we only wish that Android Market would allow us to sort comments by star ratings, so we could easily sort the "no support for device x" or "this app sucks" one star reviews from the more observant ones...
Source: Android Police