The album “Geogaddi“ by Boards of Canada lasts one hour and contains 22 tracks, whereas “Young Team“ by Mogwai also lasts one hour but only has 10 tracks. This means I can listen to Mogwai twice as much, and Boards of Canada would still beat them in my rankings. “Lift your skinny fists..“ by Godspeed You! Black Emperor only has four tracks but goes on for more than an hour. Those guys aren’t going to trouble the scorers at all, even though I listen to them a lot.
I suppose a more representative ranking of my musical tastes would be based on the actual time spent listening to an artist, rather than by number of tracks, but I can see that collecting this data would be a much more bandwidth-heavy exercise. It is clearly the easiest data to collect but to measure my attention in discrete tracks isn’t giving a true representation of things.
Matt is using MusicBrainz web services to determine an average song length for your top artists, which means his reweighting approach is not necessarily representative for the songs you actually listened to, but it’s a cool demonstration of his idea nevertheless.
Update — From the comments: it turns out back in January 2006 Andrew Conkling founded a group to lobby that idea, called Users for Last.fm song length tracking. Check it out, it has some interesting discussions!