Last.fm, one of the web's most popular recommendation and web radio services, provides their recommendations based on what "people like you" enjoy. This brings a social aspect to their system where friendships have an impact what people listen to. But what do these friendships look like? Are they localized groups having little contact with other users? Or do they actually span across the network of last.fm users?
An academic blogger, Anonymous Prof, wanted to find out.
Using the Tulip visualization package, he sampled 25,000 relationships out of a data set of 166,332 users pulled from last.fm with help from their API. From this data, he came up with 2310 seed users with 19,008 friends, resulting in 24,036 relationships and an average of 10.41 friends.
From the resulting visual graph, it was clear that last.fm's user network is actually very strong. Although there are some clusters of close friends, even those people have a lot of interconnectivity:
Along the outside of the main network, he found users who either did not have connections within the main network or whose connections were missing because he was only looking at a sampling of users as opposed to the full network. Likely, it was a combination of both. Interestingly enough, even among these outlying users, they had smaller networks of their own:
Graphing the distribution of users to number of friends, it was clear that the majority of last.fm users only have a few friends:
All this data was released on the Anonymous Prof's blog yesterday, where you can find even more images and details. Next up, he plans on collecting the listening history of users in order to examine music listening patterns as they relate to the network. Visualization junkies will want to stay tuned for that.