How does iPod know?!?!?!

I always get freaked out the way iPod can always seem to read your mood when it's on shuffle... here's the great playlist it gave me this morning:

Sonic Youth - Titanium Expose
The Visitors - Bliss
The Velvet Underground - Femme Fatale
The Smiths - London
Duran Duran - Hungry Like the Wolf
Lene Lovich - Maria
The Clash - First Night Back in London
Felix Da Housecat - Rocket Ride
Adam and the Ants - Zerox
Iggy Pop - the Passenger
LCD Soundsystem - Yeah(Crass)/Beat Connection
The Cure - Love Song

How does iPod know??!!?