Is the determination of best answer in Yahoo Answers a symptom of what's wrong in our society?

No. Before there was an Internet, if people had a question and they asked other's for advice/opinion/knowledge, they took the answer they liked best or felt was most helpful. They were just as likely to get poor information offline as could happen online, now. It's always been thus. The biggest difference now is there is a MUCH larger pool of respondents to reply, because instead of only getting answers from people face-to-face or via phone call or letter, you can now interact with people from around the world, in real time or with short delay.

Maybe they should bring back the old option of having Best Answer voted on by other users.

Best Answer is up to the Asker so what Ever the Asker thinks is the Best Answer is what gets Picked

No.

It's simply a matter of efficiency and cost-effectiveness. Let's suppose that only "top contributors" in non-polemical categories were able to vote on best answer. (This of course would require the elimination of the ability of members to move their questions back and forth between categories).

But for sake of argument, let's limit it to mathematics. If only level 7 top contributors could vote on best answers, there would be MANY questions left hanging out there in limbo being unresolved without a best answer. And the popularity of the site would decline because members here actually like the freedom to choose which answer they personally like the best.

I think that most humans prefer having their biases confirmed rather than learning something new or having their assumptions questioned. It's an ego thing. It happens in all walks of life and in every Y!A category. But occasionally there are people who are willing to put their ego aside and actually try to learn something new (and those are the people who drag everyone else forward).

Well yes it's a symptom of what is wrong, insasmuch as what's wrong with our society is it's largely populated with lazy people of low intelligence who don't actually want the truth, but rather just want to be placated or entertained.