Wikipedia and its sister sites have not come about by planning the expenditure of effort, but by describing in detail the work to be done, labelling it and giving people a variety of ways to contribute, depending on their knowledge, time, skills and confidence. A crucial part of this success comes from a goal which is appealing, attainable in steps, flexible and tangible enough to be understood by, and inspire, a wide audience. If people are to work for free, they need confidence that their work advances a goal that they admire, and that their involvement will have some visible effect.