Caroline Jarrett, The Question Protocol, How to Make Sure Every Form Field Is Necessary:
Every interaction online is a tax on people's attention and an invitation to abandon the task at hand. Progressive disclosure helps eliminate unnecessary interactions, but that's only half the job. You have to work with people within the organization to make sure the information you're requesting is really useful. Handing of a form to the web team isn't enough — you have to talk to each other.