I have gone back and forth on that topic - if someone had a super bad experience, I am sure they would post it anyway - but, I hadn't for 2 reasons - quite often a buyer gets inpatient with someone and can't wait - and ya see messages gripping about another member when there isn't always a cause - the person just doesn't have patience.
I've seen this dozens of times on The High Road and other forums.
I also am afraid to have people complaining about sponsors without be given a chance to fix the problem. We already had a troll come aboard a month or two ago and start all sorts of trouble for a sponsor. It seemed that he (the member) wasn't telling the truth, and when he started posting hate speech and cursing and name calling after being warned, he ended up having to "go."
I've actually considered such a form several times after seeing them on other sites - but I had mixed feelings for various reasons...
So, not sure... I'll have to think about that...