Last week I spoke to students at Westminster University's MA in Music Business Management (I'm always happy to speak to students about digital discovery and social media, so let me know if you run a course that you'd like me to take part in). Lots of good questions in the discussion session, including one at the end that I didn't have time to answer, which was along the lines of "How can we identify which are the best social networks for promoting music?" Here's the bulk of the answer I sent as a follow-up — please let me know if you can improve on it (or challenge it), since I know my knowledge of web metrics is less than comprehensive.
The way I see it you can answer this question with crude figures, more fine-grained measures or with hand-waving arguments. Let's take each in turn.
1 The Crude
Crudely, there are measures from the companies that specialise in website rankings that tell you how which of the social networks get the most traffic. Nielsen and Alexa (here are some old data reported here, but you can get up to the minute data yourself direct from alexa.com)
David Porter has tracked traffic for the top 10 'music 2.0' sites over a number of months (e.g. July 2007, November 2007). imeem seems to have shown significant growth, and Mark Mulligan reports that they've hit 20 million unique monthly visitors with 65,000 new registered users daily.
2 More fine-grained
It's useful to look below the headlines to work out what's really going on. Someone at the Westminster University session suggested that the whole currency of MySpace 'friends' was increasingly irrelevant when people had 130,000+ friends. Well, maybe they are, but what are the stats that show the correlations between friends and, say, online sales for new and emerging bands? If it turns out that MySpace friends aren't a good indicator of commercial success, are iLike fans of Facebook fans any better? What proportion of recommendations/plays on Last.fm lead to sales or some other indicator of fan engagement?
I don't think any of these stats are freely available on the web (if you find them, please let me know), but someone must be collecting something like this. Nielsen and the big measurement companies will probably offer some reports to their corporate clients. The social networks themselves will track as much as they can, so that they can seduce labels into licensing their music.
It's not in MySpace's interests and it's not in the industry's interests for 'friends' or other measures to become devalued and meaningless. Unfortunately every social network I've been active in has got a little parasitic mini-industry of people telling you ways to make the system work for you, improve your stats, and generally make yourself look more popular than you really are. The social networks and the music industry should work together to try and regulate deceptive activities and produce 'true' measures that actually mean something. I believe labels are quite active in using tools like Google Analytics to monitor and fine-tune the performance of regular websites. They need to be equally, if not more, sophisticated in getting under the bonnet of social networks and really understanding what makes them perform.
Finally, the hand-waving. Google found me this list of '12 of the best music social networks'. It doesn't seem to be based on any measures, but just on impressions and some of the selections are a bit odd (Sonific may be a great service, but it plainly isn't a social network - users don't have profiles and friends on the Sonific site).
Some services will tell you that some of the headline stats conceal the value of what they do - and some of them have a point about this. To take iLike.com as an example, they may have more reach than the usual stats reveal because they have people signed up not just on their own site, but also through their applications on Facebook, Hi5 and Bebo. If Google's OpenSocial takes off, there may be many more cases like this, and making comparisons may get more complex in the short term, though Google has a good track record of working out useful measures for complex situations.
I did a good share of hand-waving in my book. See especially the section on The Faultline between Creators [e.g. labels] and Intermediaries [social networks] on page 205ff. This covers the tension between the social networks who want to license content to help promote it and the labels who suspect the networks are using their content to promote themselves, and then profiting off it. I don't have any precise answers for resolving this.
As I said there, "Social networks and other intermediaries will have to balance conflicting demands to provide opportunities for promotion and also be seen to be even-handed and unbiased. Choosing what to measure, how to measure it, and how to interpret and respond to the results will be critical."