Actually, the reason I created the BOI in the first place was because someone passed me several bad checks and the ONLY thing I could do was to warn others about him so they would hopefully not have the same thing happen to them. And no, I would not allow that person to post here, but in THAT case I have first hand knowledge of the FACTS, which would not be the case in nearly all other instances. There is no judgment call on my part based on mere opinion based on someone else's evidence. I KNOW what happened.
Say, for instance, that you post a claim on the BOI about someone posting ads here scamming you. How do I KNOW, positively and absolutely that YOU are telling the truth? Yes, you can post "evidence", but how do I KNOW that the "evidence" is not forged? Anyone with enough talent and incentive can forge just about anything. Yes, you can have ten other people claim the same thing, all of which I will not personally know neither. So the "evidence" they post is still only subject to the opinions of the readers of what they are claiming. Sorry, but I am just not going to play judge here in matters of that nature. If your goal for posting on the BOI is to help others to not make your same mistake, good for you. Hopefully that will work. But if your goal is to try to get that person banned from this site as punishment for them, then I'm sorry, but this site is just not going to help you in that pursuit. Simply because we just can't work that way without being subject to substantial legal liability.
I would hope that if someone is engaging in business here and they have substantial evidence against them concerning their trustworthiness in the BOI that this would be helpful enough in preventing them from scamming others. But if it is not, well, whose fault is that? If you lead a horse to water and it still chooses to die from dehydration because it refuses to drink, do you grab that horse by the throat, wrestle it to the ground, at substantial risk of injury to yourself from the flailing hooves, and stick a hose down it's mouth and force it to drink? Or do you just shake your head, move on, and hope your next horse has a lot more sense?
Seriously now, do you have even a clue about what it would mean concerning legal liability for ANY site to guarantee, expressed or implied, that all transactions taking place are safe for everyone to engage in? If you believe that this is an effective way to run such a site, then my suggestion to you is to create your own site and give that philosophy a whirl in the real world. Make sure you budget for court appearances, though. When people get scammed, they will have your statements in hand as evidence of your liability when asking the judge to grant them relief from the damages that you guaranteed they would not suffer by using your site.
Heck, I would be interested to know if there are ANY sites, shows, newspapers, magazines, ANYTHING allowing sales by the public that offers any sort of guarantee such as you are asking here. I SERIOUSLY doubt that.