Readers around the world are presumed to know that "Dublin" is a small San Francisco suburb.

[csziggy]

7. A friend once told a supervisor about his "extensive travel in Cairo"

The supervisor was impressed since she assumed he was referring to Cairo, Egypt, but the Cairo he was talking about is a small town in South Georgia.

He could have talked about visiting Gretna or Havana and gotten similar reactions. She might have thought he was talking about Gretna Green in Scotland or Havana, Cuba - but the local Gretna is a tiny town in North Florida. Havana is a little larger and not too far from Gretna.

There are also the problems of Greenville and Greensboro - many states have one or both of those names for towns and if you don't know which state the one you are talking about it can get very confusing.

People should never assume that a city or town do not need a designation!