I ran a clustering algorithm on the artist ratings again today, after finding a rather nice library for doing Singular Value Decompositions of large sparse matrices. Without further geekery, here are the top 5 'features' it's identified in the artists and users:

Cluster 0:

Artists:
Bright Eyes
Pavement
My Bloody Valentine
The Flaming Lips
The Clash
The Cure
Bloc Party
The Velvet Underground
Jeff Buckley
Mogwai
Sonic Youth
John Peel
Sigur R?s
At The Drive-In
The Smiths
Joy Division
Interpol
The Arcade Fire
Pixies
Radiohead

Users:
stubryce
crablin
homesick_alien
proslo
since-last-summer
super_t83
face_flicker
dave_rio
matinee
marilyninthesky
thehoopiestfrood
hollywood_freak
i-deserve-to-be-in-your-band
RockNRollMassacre
jessicaconnie
feiticeria
quietcrown
Kid_A
pretty_vacant
joe_totale

Cluster 1:

Artists:
Aphex Twin
Mogwai
Cat Power
Pavement
A Silver Mount Zion
Les Savy Fav
Shellac
Boards of Canada
Neutral Milk Hotel
Four Tet
Deerhoof
Broken Social Scene
Low
Sufjan Stevens
Lightning Bolt
Slint
Animal Collective
My Bloody Valentine
Sonic Youth
Godspeed You! Black Emperor

Users:
since-last-summer
Rrrachel
atom_jack
Thought_Dreams
caribou
DrunkenPete
tedmaul
carrot_ram
RockNRollMassacre
dave_rio
jackieomotherhubbard
John_Brainlove
pretty_vacant
Kid_A
wishpig
homesick_alien
quietcrown
i-deserve-to-be-in-your-band
The_Forest_Gate
joe_totale

Cluster 2:

Artists:
The Cities
Humanzi
Youthmovie Soundtrack Strategies
Bubba Sparxxx
Brazil
Enslaved
Vega 4
John Barnes
The Great Shark Hunt
Black Eyes
Ex-Models
Bad Brains
The Radio Dept.
George Bush
MF Doom
Explosions In The Sky
Liars
DJ Shadow
Chris Morris
Busted

Users:
Mike_Diver
rossiterandy
fionapinkstars
only_shallow
Rrrachel
accidental
crablin
james_delve
commandercool
zombie_crew_1985
i-deserve-to-be-in-your-band
tedmaul
feiticeria
tiernan
jessicaconnie
homesick_alien
DrunkenPete
setyourselfonfire
wishpig
quietcrown

Cluster 3:

Artists:
Queens of The Stone Age
Million Dead
Tool
Reuben
Youthmovie Soundtrack Strategies
Nirvana
Refused
Hell Is For Heroes
System Of A Down
65daysofstatic
Explosions In The Sky
Rage Against The Machine
Deftones
Godspeed You! Black Emperor
...And You Will Know Us By The Trail Of Dead
Mogwai
Fugazi
The Mars Volta
Biffy Clyro
At The Drive-In

Users:
Wiggles
waterwings
-Raz-
roblufc
loveless
commandercool
jimff
Murder
migfreeman
radio_unprotected
AMusicPerson
jamesmacveigh
sarah_hadland
Mike_Diver
soapy
zombie_crew_1985
mart
charlescharlycharles
The_Forest_Gate
james_delve

Cluster 4:

Artists:
Public Enemy
Captain Beefheart and The Magic Band
Rage Against The Machine
Wire
Talking Heads
Shellac
System Of A Down
Green Day
Buzzcocks
The Fall
Blondie
The White Stripes
The Clash
Sex Pistols
David Bowie
The Velvet Underground
Queens of The Stone Age
The Ramones
The Stooges
Nirvana

Users:
pretty_vacant
I_AM_JAPAN
tom_damo_suzuki
9876
Martbowski
The_Forest_Gate
JDTraynor
optimist
godteri
Inhabitant
bigmanwithagun
feiticeria
jackieomotherhubbard
dave_rio
homesick_alien
Kid_A
joe_totale
quietcrown
i-deserve-to-be-in-your-band
wishpig

Some of this is a bit random; I'm going to play with the algorithm and have it normalise the ratings in various ways before doing the analysis to see if I can improve it. But not today.