Stewart Butterfield, as reported by AlwaysOn:
… the key to success in participatory media (a term he prefers over consumer generated content) is the people, not the photos or medium. The photos are just the “locus” for people bringing people together. You can’t have one without the other, and when you put it that way, calling it participatory media does make a lot of sense.
There's a tension here: that last sentence ('you can't have one without the other') doesn't sit so easily with the rest of the paragraph, and in fact what Stewart Butterfield says (play the 2½ minute Google Video at AlwaysOn) is suppler, weighted, much more nuanced — and made me recall what Jyri wrote in 2005:
The fallacy is to think that social networks are just made up of people. They're not; social networks consist of people who are connected by a shared object. … The social networking services that really work are the ones that are built around objects. And, in my experience, their developers intuitively 'get' the object-centered sociality way of thinking about social life. Flickr, for example, has turned photos into objects of sociality. On del.icio.us the objects are the URLs. … Approaching sociality as object-centered is to suggest that when it becomes easy to create digital instances of the object, the online services for networking on, through, and around that object will emerge too. Social network theory fails to recognise such real-world dynamics because its notion of sociality is limited to just people.
See also: Russell Beattie and Anne Galloway.
Technorati tags: Stewart Butterfield, Flickr, Jyri Engeström, participatory media, social networks, object centered sociality

