Its potentially important for members of the site, I agree. Say I wanted to use the name SaltySpitoon as an artists pseudonym as well as my handle here, and I was an active scam buster, and I was painted with all kinds of negative feedback from people I had picked fights with, I wouldn't want it viewable by anyone who didn't have a complete picture as a member here. If you don't have a complete picture of how the trust system works, I don't think you should have access to it one way or another.
On another note, aren't false positives just as likely as false negatives? If you aren't a member here, I could argue that you might not be aware of the practice of sock puppets leaving fake feedback. What if a new member sees positive trust from all of the scammers aliases?
My main point is that having it not visible at all, is less harmful than having it visible and misleading.
But does merely creating an account make one an expert in all of those intricacies of the trust system? Yet we're showing the trust ratings to total newbies AND we're imposing the DefaultTrust scoring on them. In fact even if newbie wanted to learn more about trust and DT - that info is not easy to find. That's also something that should be addressed both for registered users and for guests I think.
The Google issue can be mitigated to some extent by making the feedback pages non-indexable. So if someone merely googles your nick they won't see the derogatory info pop up directly in search results. They could still click through and see it but even today they could create an account and see it. Bigger fatter warning next to untrusted feedback could help. Perhaps don't show untrusted feedback to guests at all.
At any rate, since anybody can post any post or thread about you and it's unlikely to be deleted, Google can already pick up all sorts of negative stuff so I would disagree that making trust ratings public would be much of a difference. However I would like to have an option of a short rebuttal in the trust system, at least an ability to add a URL. So if someone accuses me of scamming I could say "Here is what really happened: ".