If it's optional, then don't make it mandatory
I was filling out an online form, and it gave me the option of providing feedback on the service I had received. The button was marked “optional”, but I clicked it anyway because there were one or two things I thought were worthy of mentioning, suggestions on how they could improve the user’s experience with the Web site, that sort of thing. What came next was not something I was expecting. I was faced with a 43-question survey asking me to rank my level of satisfaction on scale of 1 to 5 on each of those 43 different axes. I skipped all of those questions since they aren’t why I chose to give them feedback. At the bottom of the form were three free-form text boxes where you could make suggestions for improvement, complain about something that didn’t go right, that sort of thing. Those were the boxes I was after. I wrote up my suggestions and clicked Submit. Error: “You must complete all the feedback sections before submitting your feedback.” Wait a second. I thought you said that giving feedback was optional, not mandatory. Don’t give me this “mandatory optional” nonsense. If it’s optional, then it’s optional.
I decided not to give them any feedback at all.