My take, and it might not be a popular one.

I have to say, I think an actual D/s contract is way over the top. My stance is this: someone's word to me or mine to you should be worth more than a signature on a piece of paper. I don't need someone's signature on a piece of paper to bind me to another person.That goes for both D/s contracts, and vanilla marriage liscences for that matter (as if the government has any authority to tell me who I'm married to based off paying them a fee). All I need is my word, and my heart. In the end the rest is all for show, and nothing more but a pale reflection of those two things.

I would also say, if a sub felt the need to have a contract for the reasoning of it clearly defining what I could or could not do with her, that for me would be a very big sign that I did not yet have her trust, to a level I was happy with, most likely due to a lack of communication.