Well, that is a very interesting topic of discussion. Having gone through my doctoral work, I found it was essential to have a great relationship with the chair, the committee and my advisor. These people are there to help you through the very difficult process of getting your thesis or dissertation completed. They are there for you, not the other way around. As a result, they should help you every step of the way, as you have probably never been through the process before. Having a good relationship with all of them will make life easier for you as you are working through all of the ins and outs of your study and writing.
To give an example, one time I needed to present a followup on my study to the Human Studies Approval Committee. I worked full time, so could not attend the meeting. As luck would have it, one of my committee members sat on the HSAC. He sat in for me and ...
This response discusses the advantages of maintaining a positive relationship with a dissertation committee during the graduate school process.