One of the interesting things about all these different social music sites is the different sorts of charts they make of your listening habits. I’m much more taken with the ones that attend to actual listening or collection contents than the ones where you list the bands you like (as on MySpace) because it’s a bit less open to gaming (though certainly people leave their computer playing something cool while they’re out so they will appear more cool to the outside world, or turn off the plugin when they listen to something embarrassing). So it’s fun to compare the different kinds of charts the different sites generate for you.

Last.fm: Everything you’ve listened to (since you signed up and started using the plugin) that its plugins capture. You can look at it by overall artists, albums, or songs by the week (any week), or rolling 3 month, six month, or year charts. There are some problems (of course) — some listens don’t get captured, like if you listened to your iPod then on your computer without updating the iPod it loses the iPod listens or if you stream radio from something other than Pandora (it can now listen in on Pandora with a plugin), and the site is slow to learn about new albums so the artist charts tend to be more accurate.
iLike: Sucks up the whole iTunes history by most-listened, so you get an overall chart that goes back as far as your iTunes library. If you don’t use iTunes, too bad (for now), and there’s no ways to vary the charts by time period, though you can look at artists or songs. Since it gets everything on iTunes, for those who use iTunes and only listen to that and iPods, it’s pretty accurate.
MOG: Sucks up the iTunes library and sorts it by the number of songs, and gives most listened to this week, but doesn’t give overall most listened to charts. On MOG, it notes that I have more REM songs in my catalogue than Madrugada songs, whereas on Last.fm that information is lost, but it knows that these days I listen to Madrugada three times as much as I listen to REM.

All of these have their strengths, and it’s amazing how, once you’ve got personal charts, there’s no going back. It becomes an essential part of understanding your own musical taste and, for some anyway, an essential part of self-presentation to others (Last.fm gives you code so you can export a variety of chart types to any web site, iLike and MOG let you export your chart to MySpace).

But what it’s got me thinking is, for all Apple’s brilliance, why isn’t this stuff built into iTunes? How much cooler would it be if we could use the music libraries on our computers to display wide varieties of charts and export them to websites with ease.