An exemplification essay should give enough examples, but avoid overloading with examples just to list as many as possible.   It should include a fair a range of examples. An essay that exemplifies traffic hazards should not include only examples in your hometown. Give examples of interstate junctions in major cities or hazards of large stadium parking lots.    Also, examples must be representative, not cherry picked. (e.g.) “Fast food restaurants are always dirty. The McDonald’s  down the street, and the KFC across from it are filthy.” Those examples represent only one area in one town. Has the writer ever left his homtown?