I think you could only vote if you were a part of the jam. So no 10 friends. Some people do mistakenly assume that visibility equals high rating, but that isn't necessarily true. I mean, this point system isn't perfect because 5 stars is a subjective measure and people have different views of what "3 stars" mean.. but any solution that benefits high rating numbers above anything else is just turning it into a marketing contest.
to me thats also the big thing, we could only vote, which meant other people, who wanted a better chance, would be faking "good" reviews and then 1 star bombing, its already been shown some people/devs have done that (they did get banned I think which is good but still!)
also fair, its always tricky to get a rating system right