I just recently finished reading Who Wrote the Dead Sea Scrolls? by Norman Golb. Golb's thesis is that the manuscripts found in the Qumran caves are not the work of the Essene sect, or of any single sect at all, but that they are the manuscripts of the Jewish community itself, stored in caves for protection during the First Jewish-Roman War. The general consensus of scholarship on the Dead Sea Scrolls has identified them as Essene writings since they were found in the 1940s, and although Golb exposes dozens of holes in their theory and masterfully argues for his own with a wealth of evidence, his contentions were largely dismissed and neglected for years.
The reason I bring this up is that it's a perfect example of when scholarly authority goes wrong. Even when the proof can be right directly under a person's nose, they may still miss it or deny it. In the book, Golb illustrates a number of ways in which the prevailing Dead Sea Scrolls authorities (Roland de Vaux and his team) suppress alternative theories and play media games to destroy the reputations of their opponents. The movie Expelled is a farce, to be sure, but the fight for the Dead Sea Scrolls is just that type of 'academic conspiracy'. It's astonishing to me the lengths people will go to in order to defend their pet theories, but it certainly does happen.
Appeals to authority can be dangerous oversights. One of the major criticisms leveled at Golb was that his theory was outside the mainstream opinion of the academia. In other words, 'all these experts say this, so how can they be wrong and you be right?' I hear this same sort of thing when I question the historicity of Jesus. Popular consensus does not make any idea correct though, what matters is the evidence that the consensus is formed upon. In the case of Jesus, the evidence is very slim and very suspicious, and when the 'authorities' on him are often theologians with a deeply vested interest in the historical reality of Christ, it's easy to see why appeals to authority have to be taken with a grain of salt most times.
There is something to be said for authority opinion, however. Generally speaking, you want to learn or be assisted by those who are qualified in the issue at hand. You probably wouldn't trust a plumber to advise you knowledgeably on open-heart surgery. This is part of the reason I don't trust preachers to discuss evolution from a knowledgeable standpoint. I'm not saying that everyone needs to have a degree to have an opinion on something, because many people do take their own time to research subjects they have an interest in. That doesn't mean they are as well informed as they like to think though, especially if their 'research' has been limited mostly to one side of the issue.
So authority opinion only goes so far. When it comes to evolution vs. creationism, I will give more weight to the opinion of a biologist, simply because they have made a career - often times a life's work - out of studying nature, not just from a layman's perspective, but from an objective and methodical perspective. What ultimately matters, though, is evidence. For this reason, I always try to steer clear of appeals to authority when I'm making a case for evolution to those who are unsure of it. Noting that 99% of scientists agree with evolutionary theory is like saying that Isaac Newton and Albert Einstein agreed with the theory of gravity. It's nice to know, but it doesn't really mean much unless you explain why there is this agreement.
It's tempting to point to the consesus of authorities, because it's usually so much easier and much less time-consuming than learning the evidence for yourself and knowing how to express it to others. But I find it infinitely more respectable to have a discussion with someone who can make their own statements, rather than someone who makes generalized appeals to authority. I find it frustrating when a person I'm debating with offers up a book as evidence for their viewpoint. 'Have you read The Case for Christ? It addresses all your questions.' If I haven't read the book, am I expected to go read it and suspend conversation until then? Even if I have read it, I'll lose some respect for someone who relies on others to do the thinking and debating for them. (I have read the book, and no, it doesn't answer anything!)
It's definitely worth it to learn the evidence and the argumentation for yourself, I'd say. It's more rewarding intellectually, it generates more respect, and it's the only real way to be persuasive. Appeals to authority do have an appropriate context, but I will never swap critical thinking for them, nor should anyone else.