But there are things most of these tools can't do, and that is analyze data when it's structured as a graph or network and when that data must be analyzed by traversing the graph. […] This problem can't be solved by simply summarizing data, nor does it have anything to do with predicting. Instead, the data must be organized as a graph and a tool must be able to traverse that graph; it has to be able "walk" from node to node. And today, this is not a feature found in most reporting and analytical tools.
via NoSQL databases