"Earlier research has shown that the distribution of links to web sites approximates a "power law" (Science, 286; Nature, 401), where a small number of sites receive the majority of links, and most sites receive very few links. The distribution has been attributed to a process called "preferential attachment", wherein new links on the web are more likely to go to sites that already have many links. "

Winners don't take all: Characterizing the competition for links on the web [David Pennock, Gary Flake, Steve Lawrence, Eric Glover, C. Lee Giles; NEC Research Institute]