63 million songs were played 22 billion times through Facebook Open Graph in 14 months

"The launch of Open Graph last year enabled app developers to re-think how people discover, share and consume music. Most important, many developers have brought what was traditionally only possible offline - music discovery through friends - into all types of music apps on web and mobile.
Since launching Open Graph last September, 62.6 million songs have been played 22 billion times -- that's about 210,000 years worth of music. This is happening across all types of music apps, from apps that are tailoring music to your tastes, to apps that recommend music based on the time of day, where you are and what you're doing. Here are some music apps taking off."

Source:  Blog post by Facebook, 6th November 2012