When it comes to selling homes, you have to expect people are going to want to low-ball you for some properties. I have found myself saying no to offers quite a number of times. I ask a bit above what I am willing to take expecting people to want to put an offer in at less than what I am asking but I have had people try to get as much as 70 grand off of what I was asking before and that is WAY too much. So I find myself saying "no" a lot.
I have said no on my own behalf and no on the homeowner's behalf. There have been cases when the offer was really good and the homeowner just didn't want to settle for anything less than their asking value.