Ask HN: First SeeqPod, then Grooveshark, now Spotify – Why different outcomes?

Music streaming services were the next revolution after Napster, eMule, Morpheus, Kazaa and other P2P providers.

SeeqPod was bought out by Sony, Grooveshark now is shutting down and Spotify is leading the pack. Why are the outcomes so different for the same business models?