I have read two interesting books lately, “Linked” and “The Tipping Point.” Each of these using links and networks to understand human and biological networks. In a fascinating twist on how one could use this information for a good purpose, see this article. The researchers who wrote the article proposed vaccinating a small proportion of the population and then asking them to name friends. Since people who are likely to have many relationships are likely to be named many times, they would them be immunized and then that could contain the target disease. Fascinating.