Yep - the thing about these numbers are that they're obviously based on registered users, not active users. For example, which Spotify may have 33 million users

Yep - the thing about these numbers are that they're obviously based on registered users, not active users. For example, which Spotify may have 33 million users, only 20 million of those are active. Pandora may have an impressive 150 million registered users, but I imagine the drop off rate of active users is relatively high given the increase in popularity of other services.