Somewhat offtopic, but why is there an obsession with music discovery services? Soundcloud has its own niche in terms of sharing and usage, but other services like 8tracks and Slacker seem rather unnecessary. Is it that hard to discover new music on one's own?
Depends on how you want to find music. As a DJ, I actively dig for new music a lot. It is nice to be able to throw on some service that gives me a "radio" to passively find new tracks as well. I also suspect for most people "fresh direct" consumption of music fits into their view of how new music is found.
Because the user-created playlists seem rather low-quality. Half the "indie" playlists appear to have bland mainstream radio music. Maybe I'm not the target audience for these apps, but friends, 4chan, Pitchfork and Spotify seem to be the right combination for me.
Well if soundcloud was not around it just wouldn't be possible to keep up with the 600+ people I follow and even then a solid 50% of what is on their page is just stuff they like as well which introduces me to more people.