[wrekkuh]

I'm not sure how much of this is conjecture. My thinking differs from yours with respect to the following -

"Albums don't really have years either. Or at least they have publication years. The songs have years. Normal studio albums have a common year. Compilations and soundtracks do not."

An album that is released by a record label does have a year, as upon release it becomes a publication. By this train of thinking i would also say a soundtrack does have a year, too, as it is published as a collection timely to the context of its release. The same can be said of compilations, as they are a contemporary release.

[qbrass]

Yes, but you're usually more interested in when the song came out than when the album came out.

If you sort your playlist by date so you can pick songs from the 90's, you probably wanted to hear something like Nirvana instead of The Best of The Who: Volume 3.

[adamzochowski]

I agree that year is screwed up, but some taggers (like the picard-lastfm tagger) reads also decade feel tags. So music that sounds like 90s is tagged as 90s music, even if it isn't recorded in 90s.

For example, ""La Roux -- In It For The Kill"" will get the song tagged as sounding 80s like:

http://www.last.fm/music/La+Roux/_/In+for+the+Kill/+tags