Use case diagrams are helpful during the definition phase of a software project. AstadeDraw offers a drawing interface which is implemented as a “bouncing tree”.
This gives an automatic layouting of the drawing. This results in a very fast drawing process. You can interactively design use case diagrams on a projector together with the marketing people.
Because AstadeDraw is fast and has the look and feel of a “computer game” you may manage to get marketing people to specify their needs (No guarantee, but it might work ).