What are examples of experts who, in the end, are really not experts?

I don't know about other fields, but in science, expertise is way overrated, indeed it's frowned upon -- by scientists. The public may still think scientific expertise amounts to something, but scientists as much more skeptical of the term.

Here's a now-famous example of an "expert" who wasn't:

http://en.wikipedia.org/wiki/Sch%C3%B6n_scandal

The biggest irony is that this question is being asked on Quora - Where this phenomenon can be seen very frequently.