It seems that Spotify Social was a counter move against a future competitor, Rdio. The founder of Kazaa and Skype, Niklas Zennström, has probably carefully studied Spotify and taken strategic decisions on how a music service could be more social. The front page is more intuitive when you are interested in exploring new music. In my case, I have added people with similar taste of music. This is also a strength that Rdio has, it is difficult to find people with similar taste in music in Spotify.
They have designed a more social browsing experience where users can easily gain an overview of other users who listen to the same thing as oneself. I have found interesting music by being able to see which users are listening to the same albums and browse further. The difference between Rdio and Last.fm is to just press play to hear the music. Rdio also presents albums and not just individual songs when you browse. It has the ability to add albums and songs in a collection (in addition to playlists) while Spotify users struggle with starring songs and create playlists without folders to keep track of the music they want to listen to again.
Spotify has much to learn from Rdio if they want to break into the U.S. market. To offer any kind of freemium is not enough, now users have been spoiled in the U.S. with a good browsing experience which Spotify must catch up on to succeed.
