If you want artists similiar to something popular (Like Arcade Fire, or Broken Social Scene, which are both consistently in last.fms top 200 charts, above artists such as Kylie Minogue and OutKast) then maybe Pandora is your best bet, though it is a ridiculous, pathetic, flawed, stupid system. Actually, your best bet is probably to contact Arcade Fire and Broken Social Scene and pursuade them to set up their last.fm accounts properly. Bands or labels can weight their own recommendations (A feature introduced to solve the 'Bob Marley Dilemma', ie the old situation where Bob Marleys top similiar artists used to be The Beatles, The Rolling Stones, Pink Floyd, Jimi Hendrix and The Doors). Anyway, if you are expecting similiar artists to produce music that sounds the same, you misunderstand how the last.fm system works. Last.fm works by what people listen to. Similiar artists are calculated by an algorithm that collates the number of an artists fans that listen to another artist, and weight them by their popularity on those peoples charts. This is why recommendations become less finely tuned the more popular an artist gets. Once bands start being listened to by the kind of people whose charts are recommendation lists written by Pitchfork, NME, the Billboard Charts or some such source, then they obviously get confused with similiarly popular artists.
The solution is to be more indie.
