The need for them to be a record label is not for exclusivity, it is so they can operate as an equal partner. At the moment their entire business is based on negotiating deals with record labels, all Spotify can offer is revenue, so they will be squeezed and squeezed as each contract is negotiated and renegotiated.
Every artist that signs up to them will save them this cost in the long run... So I'm sure there'll be seemingly crazy deals like comedians have been striking with Netflix, which in the long run are will be very beneficial to Spotify.
My only issue here is that I'm not sure if existing labels will begrudge a new competitor on the block (and then try to kill Spotify). It doesn't seem to me like Spotify being a fellow label gives them much more that the existing labels would want, but maybe I'm just not thinking of it.
According to my memory and a little research [1], the record labels have some stock stake in Spotify. Personally I think this is Spotify's best bet: if the labels can derive stock gains from helping Spotify (plus licensing fees), they have skin in the game so they won't try to sabotage Spotify. I'm of the opinion that instead of trying to produce music (and fight the record labels), Spotify is better off getting into a complimentary position: make it easier for fans to find out about concert, purchase tickets at fair prices, and buy t-shirts. All stuff that Spotify can probably do better than the record labels, and which won't cut into label profits.
[1] http://www.swedishwire.com/jobs/680-record-labels-part-owner...
With Netflix, my reaction depends on if I watched the content before it was removed.
With Spotify, it's almost always rage.
Why? I often listen to music more than once but I often don't watch movies more than once.
I have this problem with Spotify. About 80% of the music I like is on Spotify. Private label, soundcloud, older forgotten bands, and foreign music is often missing.
If like me you like composing playlists instead of playing one full album at a time then not having the vast majority of your music available on a single service is a huge deal breaker. When I hear a song out there and I want to add it to my playlist I expect that it will be available on Spotify and the vast majority of the time I'm right.
If I need to go hunt for songs on various services and I can't easily make a single unified playlist with all of it I think it'll be back to piracy for me, it won't be less convenient and it'll be much cheaper.