Ok I am sorry if this would be a rep/thanks system. Although I don't really think so.
But you should be able to rate a members IP on trust like on a 1 - 5 scale. Such as when you first sign up, you start at level 3. Then say someone gives you a 5, you would then be moved up to 4 because the average of 5 and 3 is 4. And as more and more people rate you it becomes more important. And a member should only be able to rate a person once, but they can change the rating that they gave them. And it would be tracked by ips, and even shown in a rating history showing who rated them and what was their rating.
And the reason it would rate the ip is so some one cannot just make a new account and start fresh again. So basicly if you have a trust of 1, every account you make has a trust of one. Again sorry if you think this is rep/thanks but I disagree. I think it is a lot better then rep because rep can just be "oh this guy helped me" and such. But this shows if a person can be trusted or not. Tell me what you think and if this can be done.