Currently the rating system on YouTube is a disaster. About the same number of people rate videos as the number of people who comment on them, which is ridiculous because commenting takes much more energy than the one click of the mouse it takes to rate something.
Their "top rated" video section is a joke too--it has 25 videos on it, all of which appear to have the same rating of 5/5 and none of which look particularly enticing. How should Google fix the current mess? I have a few suggestions:
1) Ever time a user rates a video, it should be recorded on a list that can be made publicly accesible. Imdb has this kind of a "vote history" list and it's awesome. Somebody can quickly scan my list and see if I am a big idiot or whatever. Alternatively, they could show the ratings on the "my favorites" page, this kind of a list. If you have a record of all the ratings a user has made, you give that user an immediate incentive to start rating videos.
2) They need to switch to a 10 point scale, and show the actual number out of 10 that the video averages. Switch all of the current votes of "5" to "10", "4" to "8", etc., and then let users tell you which videos are the best. It's hard to tell exactly what the rating is with the status-quo 5-star metrics.
3) There should be a larger list of the top rated videos, perhaps organized by section. These should be computed using a formula where videos with more votes get weighted higher, just like it is done on imdb. They could even call it the Top 251; I don't see why they should be bashful about copying the success of others.
Why does this matter? Because right now the only criteria that you can use to watch good videos is views, and watching movies based on views causes a nasty feedback effect. How do you take a view back if you don't like the video?
I think it would be cool if there was a way to aggregate the best videos on the site so that we would know what to watch instead of relying on random e-mails. Google, you have so much potential here with YouTube. Make it happen before somebody else does.