Speaking about the important role of social sharing of music to the growth in Spotify's subscriber base, Ek told Grammy.com: "We look at the sharing of music as really, really important for our business. We've found that the more social our users are, the faster they grow their own music library. [And] the faster they grow their music library, the faster they become paying customers. That's really the rationale for us -- not really the marketing side, but we feel ...