As I said before, any content that is missing is normally down to the record label or rights holders with holding those tracks from Spotify, sometimes to push up physical and download sales. There are also some big names, such as AC/DC and Led Zepplin who have chosen not to be part of Spotify.
Any content that has disappeared or been removed (the tracks will still be in your playlist, just hidden because they unplayable) is normally down to the record label or rights holder. Sometimes content is removed due to licensing changes, transfer of ownership or due to a request from the content owner.
Spotify upload all music which is made available to them for our enjoyment! I would suggest you have a read at the missing content FAQ as it will probably answer most of your questions!
One of the community staff members posted before:
"The reality is that we would like to have all the world's music available on Spotify. Therefore, anything which we have the right to upload and has been provided to us, should be available on Spotify.
If you still can't find the music you're looking for, try contacting the artist or record label and ask why the music isn't on Spotify."
There are also some big names, such as AC/DC and Led Zepplin who have chosen not to be part of Spotify.
Nor on other streaming services like Deezer, Rdio, Simfy or Last.fm, and e.g. the same is true for The Beatles. Pink Floyd is available here and there, e.g. on Rdio for free, but on Deezer and Simfy only for Premium subscribers also depending on the country you live in. Metallica is available on Spotify, but not on other streaming services, so it always depends on the individual deals the band managers/copyright holders have with different legal services. Of course there are some services which base their catalogue on illegal user uploads without paying for the copyrights, but these should not be counted as valid alternatives.
I am still baffled by the fact that all this guys (AC/dc, led zeppellin,etc) are on Pandora, both free and the $3.99/mth version, they are also on Iheartradio which is totally free, so again,why are we paying $10/mth???
I can't tell anyway, as Pandora, iHeartRadio and Slacker give me "not available in your country" errors all the time living in Germany. I would say if you have the choice in the US, use another streaming service which offers what you want. As far as I know, Spotify is for free in the US with no time limit, so you don't even have to subscribe - except if you want it on your mobile phone or the 320 kbps streaming option.
By the way, why is this thread in the web player forum?