I have spent a bit of thought trying to work out the best way of rating my iTunes music. Most of it I haven't rated, or have rated only by album. It's mostly an academic question, because there isn't much you can actually do with the ratings once you've stuck them in.
At first I found myself rating everything as three stars or more. I thought, if it's rated less than three then why not just delete it. Those were times of precious disk space for me, but it does make sense in general. Scrolling through a whole lot of junk music is a pain, even if you've got endless disk space. Not mention that obsessives like me obtain a great deal of satisfaction from having a neat music collection, with all the ID3 tags in good working order.
So I thought I need to reinterpret the ratings. Normally one star means something is shite. In my case I wanted one star to mean "just good enough not to get deleted". So I started doing that. And it worked pretty well. Most of my playlists drop stuff with one star, but the music is still there if I want to listen to it - which occasionally I do.
I also thought about the top rating - five stars. Should I keep it reserved for only the best, life-changing music? Should I assume that music goodness is uniform and give five stars to 20% of the collection? Or is it some sort of normal distribution (or something non-symmetric but similar)? Tough questions I know. Should I worry about trying to make my ratings comparable to other people's ratings. What about rating inflation? Will I one day need a 6th star? And when I'm in a good mood I'm likely to give everything good ratings. I find that every time I really enjoy a song I end up giving it four stars because giving it five makes me feel like a rating floozy, and giving it three just feels mean. I suspect there's a decided spike at four, and this troubles me.
Another problem is that I never take the effort to rate anything that I don't like. So everything has four stars or no rating at all. Which is totally useless. I've started bulk rating whole albums, hoping that over time I'd use some Bayesian logic to gradually make each song rating more appropriate. I did this just to get some data in there but it isn't very satisfying.
I'm inclined to think that I should maintain some sort of histogram and try to ensure that the ratings distribution sticks to something reasonable. Perhaps just a uniformish distribution. Hopefully, I'll subconsciously adjust my ratings based on short-term distortions in distribution over the long-term it stays reasonable.
Clearly, plenty more thought needs to be done on this. Although I can't help but wonder if my life would be better if I completely removed the whole rating column from iTunes altogether.