Photography is such an accessible hobby that lots of people have experience of it in one form or another. People have very different impressions of the work a photographer does, what he or she can achieve and how easy that should be. Trying to navigate this minefield as a professional is a tricky business and the expectations or assumptions people make can lead to misunderstanding and frustrations on both sides.
If you really want to pop that vein on their head, here is an infographic from Print-Print.co.uk that lists 10 sure fire ways to push their buttons.