My site, http://Like.fm, is compatible with Last.fm's API for scrobbling and many services are already supported including YouTube. Adding support for music players is relatively easy, especially when considering Last.fm has already made the idea of scrobbling a commonly understood idea.
Spotify will be a problem for Last.fm IF they can continue being free for everyone, and convert everyone to their service. Otherwise a decentralized social network will have that advantage from being able to collect more users faster.
Spotify will be a problem for Last.fm IF they can continue being free for everyone, and convert everyone to their service. Otherwise a decentralized social network will have that advantage from being able to collect more users faster.