mbmjlm, I disagree with you. I believe that there are plenty of ways for Ancestry.com to assist you in evaluating your parent to child quality. (But, I don't think there is any arbitration needed, the quality indicator is just a stat related to what other tree-makers have rated the connection. Nor do I think a program should be rating the accuracy, just other tree-makers in there own trees.)
For example, if all parent-child relationships started out with a null "quality indicator", then every tree maker would have to go out of their way to participate in rating the quality. Ancestry.com could share with you how many other trees actually rated the quality of your ggrandfather as son of your listed gggrandfather and how many trees were certain, somewhat certain, not sure, and just a guess. This would help you identify what confidence level the more "quality-conscience" tree maker has in your connection.
Also, the quality rating that you assign will help you see visually the quality (and weak branches) of your tree.