Appeal to authority is a means of debate where the opinion or findings of an expert are used to support a position. There are good ways to appeal to authority and bad ways, too many people often resort to bad ways.
One common theme of bad appeal to authority is done with the use of a compendium of quotes such as Bartleby.com
and a quote from some famous person is found and then trotted out as if that proves the proposition being debated.
What is interesting is such appeals are usually from one of a few people. Gandhi, Einstein, Jefferson, King, and Franklin. The problem with such appeals is they often address issues outside of the area of expertise of the person being quoted, or, there is some fact of the famous person's life that contradicts the quote and the way it is being used.
For example let us use the imaginary expert on snail parasites by the name of Samuel Fogel. You are tasked with a research paper on the snail parasites of Lake Victoria and in the paper you state:
According to Dr. Samuel Fogel's research, one should not swim in Lake Victoria due to the presence of the snail fluke XYZ. Research and medical observations in the Lake Victoria indicate the fluke will infect humans hosts causing....
Such appeal to authority is in now way abusive.
However try this:
Dr. Samuel Fogel (who was awarded a very prestigious award last year) is on record saying that the policies of not requiring us to wear red hats on Tuesdays are harming our nation's ability to develop its IT industry.
Remember, Dr. Fogel is an expert on snail parasites not national industrial development. Now, my example is silly but the point is Dr. Fogel's opinion on this matter is no more or less credible than any other schmoe on the street. This is not to say Dr. Fogel doesn't have the right to express his opinion this is warning not to automatically grant credence to that opinion.