Streaming music just took another step into the mainstream, with news that Billboard has started including data from Spotify, Rhapsody and Rdio into its Hot 100 chart algorithm. Slacker, Muve Music and Mog are also included. Billboard’s editorial director Bill Werde tells the Wall Street Journal that the services are being added now because they “have only recently hit a critical mass” among users. Is it a big deal? Apparently in tests in recent weeks, the differences in the Hot 100 chart when streaming is and isn’t factored in are ‘subtle’ – certain songs are boosted, but the chart as a whole isn’t greatly different. YouTube is apparently in talks with Billboard to add its own data, but for now, the six streaming services will contribute data from just under 500m song plays a week, according to Nielsen.