Who can help you formulate a clear, simple and defensible dissertation project? Clearly, that is what committee members do for their students. But, committee members and chairs typically are not that helpful with the “up front” work required to figure out a good dissertation question to ask.
Who can help out then? Perhaps you believe the only people who can be helpful are colleagues who are familiar with the field. After all, they are generally familiar with the research and what type of dissertation your committee members are willing to accept. There is no doubt that committee members can be very helpful.
What about your friends who have little interest in scientific research? Should you even bother talking with them about your dissertation? Would they really understand the complexity of it all? I say yes.