For those who haven't yet read The Tipping Point, it's a controversial bestseller that tries to get at the causes of epidemics -- social, economic, infectious disease -- with the goal of providing marketers with some serious ammunition in their efforts to make their products stick in the minds of consumers. One of the concepts Gladwell introduces is something called the Law of 150, which basically states that because the human brain has natural limitations on the number of relationships it can track, groups are most effective and functional when they contain no more than 150 people.