Spotify is getting serious about building its audience in the U.S. The London-based music-streaming service said today it's introducing an online-radio feature to its music offerings, a move that competes directly with Pandora. Spotify's initiative is likely to push the crowded market of streaming-music providers – which also includes Rhapsody, MOG, Rdio and offerings from giants like Apple, Google and Amazon – into a period of consolidation. As popular as cloud-based music is becoming among consumers, it's proving to be a good way for companies to lose money.