It is well known that eBay has a system necessary for managing personal credit scores based on the buyer or seller's response: +1 (positive response), 0 (neutral response), and -1 (negative response). The sum of those responses represents one's credit level. This is useful for preventing fraud - both seller and buyer. In addition, PageRank is one of the most famouse computer algorithms in the Internet Era (or maybe in the computer history) due to the popularity of Google.com. I got an idea that if we merge both systems above. For example, if one who has a higher credit level and he/she positively responses to other seller/buyer, then the seller/buyer may get more value (e.g., +2,.. depending on the credit level of the scorer) than +1. The negative response also works in the same way. The credit level must be computed in a recursive way. This may be a burden, but, in my opinion, gives a better system for estimating one's credit level.
Let me know if you need more discussions.