It is always a sign of someone adept at a certain knowledge domain if they can cite a large number of researchers who are active in the area. It is important that they not only be able to cite individuals, but also teams in this age of large sets of collaborators, or that they can cite the specific work coming out of a particular lab. It is through contact with these established experts that students and those who apply their knowledge develop their own careers and expertise in the area. This shows the utility of such a comprehensive survey.
We have found that each ISP seems to have its own population of workers, many of whom have spent their entire lives working on that one particular ISP. It often takes a large team and a lifetime to develop a good understanding of the dynamics of an ISP. This is especially true when the domain of the ISP crosses all disciplines as they do by definition.