Excellent diagram of the development of Twitter called the Twitterverse. Thanks KatyKat.

May be possible to extend the exact cover problem into Zahid's data perturbation algorithm using A Sudoku Solver in Java implementing Knuth’s Dancing Links Algorithm

Good diagram on Identity, Reputation and Trust. I need to analyse it to see if the literature agrees.

Wiki and blog for Building Reputation Systems.

Roger Clarke's Annotated Bibliography on Identity.

Jeremiah Owyang's blog post on Running List of the Five Eras of The Social Web