One of the elements of Shannon's general model of communication is noise. Here's an interesting article about Online Noise.

I was looking at an old post 10 ways to keep online dialogue on topic by Alexandra Samuel found after watching the Gruentransfer. I realised the anti-ads were an example Culture Jamming. I've been thinking how to handle virtual workshops for distance education students. Maybe if I could get them to use a Presence tool such as those developed using the Extensible Messaging and Presence Protocol. If a sufficient number of students indicated they were present and I was also "available" I would hold a class. The agenda could be developed like an Unconference or something formal already prepared. The group size necessary to activate the class would be a quorum. Students would be welcome to gather in the virtual space but I would choose to start the class.
Interesting presence ideas

I think I'm interested in Reality Mining. This is a form of Data Mining but analysing people's behaviour in real-time.