Any time you're working with information, which tends to have hierarchical relationships and classification schemes. And usually a particular type of thing can

Any time you're working with information, which tends to have hierarchical relationships and classification schemes. And usually a particular type of thing can belong to many different hierarchies, so you can find a type, and then traverse the graph among all hierarchies that type belongs to to find results. So you can easily take something, find it's type, indicate what target type things you want to understand it's related to, and get a result. And this can all be done on the fly. Doing this with the incredible number of joins you would have to use with rdbms would be unfeasible with changing hierarchies. The other REALLY big advantage, the data model never changes! I literally let the graph, to a certain extent, write the code (that is, code is generated based on graph relationships on the fly) And finally, you can have everything in the "same" location, you are always working with an "information" lake - no need to have many many different tables.