I think every project needs white paper, it is answer for all questions, and it is the document which enables us to assess project.
White paper is really important because all the information in a project is here. So before you trust a project read their whitepaper to know what their goal and the road map because everything about their project is described in details to their whitepaper. Beside of that check also their member because if many higher ranked are participants then it means they trust that project.