I think you got to look at it this way. A machine will end up where it belongs in time. If people see a machine and think it's too high on the list, they will vote it down. Same goes the other way around. So given enough time and a high enough sample rate a machine will settle at the spot it belongs.
And because Pinside compiles a list only every week, this process goes in steps. People see a machine rated too high, lots of people will vote it down. The result is that next week it will be too low, so other people will vote it up. Given time the sample rate will go up, meaning that the steps will be smaller each week (because individual votes don't influence the score so much anymore). I don't think this necessarily is a bad thing, like most things in life it just takes some time for a machine to find its rightful place. In the end it will...
I agree with Gweempose however (other topic), that if a machine has received below a certain amount of ratings, it should been shown somewhere that it's new, so that its rating should be taken with a grain of salt (as all ratings really, but that's another discussion).