Ratings
The Ratings screen can be used to view the Auction ratings of anyone that has bidded on an auction.

Players with a negative or 0 ranking may indicate players that have not paid in a prior auction or tried to get out of paying.

While this does not mean that they will not pay again in the future it does mean that if you have a choice of two buyers and one has a good rating I would pick the one with a good rating as your less likely to lose out.