A few years back people thought that you had web sites or web applications. The web was either a repository of information... giving you information architecture as a design discipline to make sense of that... or it was a new software interface and about interaction with software, not just pages of content... giving you interaction design and a bunch of other stuff.
Now, we all know that the web is about people and is a massive, new, and untaped communication medium. But that concept is not covered entirely well by either information architecture or interaction design. To bring in all the complexity of massive inter-human interaction we need to think in different directions. Hence Social Interaction Design.
There's a guy in the states talking a bit about this, Adrian Chan (www.gravity7.com/blog/media/). Plus I would be happy to speak about it or run a panel or something.
