Is there a diagram of how social tags work?

In  the next few weeks I'm giving three talks about transliteracy and folksonomy - a seminar for my colleagues at De Montfort University, a paper at Interfaces: English Studies and the Computer, Newcastle, 3/4 November, and a talk at the Leicester Cafe Scientifique, 8 November.

However, I'm getting a little worried because as part of my talk I want to give a simple visual guide to how social tagging works, and what I'd really like is to be able to show a nice plain diagram. However, I've hunted around and can't find anything like that, which seems rather odd. Surely someone somewhere has produced something like this? I'd much appreciate recommendations from anyone who knows of such a diagram.