I would think, though, that in the case of a poorly run co-op, if someone wasn't brave enough to say something when the vendor tries again, they probably wouldn't be brave enough to leave a negative review. I also thought Dave was proposing more of a thumbs-up type of arrangement and, in that case, would that be of any help? I am thinking that there would be no feedback left at all in the case of the wayward vendor. The way it is now, I feel that there are a lot of good folks here that actually would step up and ask directly if the vendor had resolved his/her issue(s) when they re-listed (or at least post a comment along the lines of "aren't you the guy/gal who had so much trouble with a co-op before? You poor thing, you must be brave to be trying it again" or something along those lines that would act as a "gentle" red flag).
I know that before I would be willing to join a co-op with someone new to me, I would click on that person's name and peruse their past postings to see how their past co-cops went. But perhaps I am unusually cautious ?