Except Spotify isn't for discovery and virality. What your talking about is getting people to discover music. Usually done through blogs, social media, youtube. But when your talking about a service like spotify which is really a one dimensional store for storing, putting music on your mobile device that doesn't drive merch sales or concert tickets or even fans then they should be paying there fair share to artists. Granted maybe with FB open graph integration this is changing. And of course this isn't just a Spotify problem this is a label problem (of course now they're one and the same). Anyways the question isn't whether giving your music away for free or not is a good idea -- The question is why isn't Spotify doing what they say there are there to do?... Pay artists.