Reach, influence, authority…what do they mean in social media? Unlike traditional media where reach may be the easiest of the three to quantify (add up subscriptions and pass-alongs), reach in social media is a very tricky thing to measure. We (SM2) rank authority based on existing measurements like Pagerank, Techorati and Alexa, inbound link counts, etc., but authority is different from reach and influence. A blog like Valleywag might have a huge reach but very little real influence (because it’s basically a satirical source not one people go to when making decisions). Influence is built on a strong reputation and track record, things that are built over time and difficult to measure through algorithms.
Reach in social media is a pretty interesting thing because it can change so quickly. Someone inside a company who decides to blow the whistle on some bad activity via Twitter can go from no reach to huge reach in hours- and just as quickly fade when the story becomes old news and is superceded by the next big thing. The rise of a meme, or virally transmitted idea, is a unique characteristic of social media, driven by the one-to-many nature of the communication stream and the network effect. And the speed that a meme can be distributed becomes a very real issue when it comes to brand and reputation management.
If a measurement service claims to offer reach statistics I’d be very wary for the reasons cited above. Unless they have real time access to a social media source’s traffic analytics, which is not the case much of the time, measuring and reporting reach is problematic.
So where does this leave us? You could say that Authority + Reach = Influence. Since reach is variable and tough to measure, influence-ranking is equally hard to do. Cracking the reach measurement challenge will mean a big change in our whole world, however because of privacy issues we may never see it.