An example for an edge case is a minus sign at the beginning of a line.
- Why would anyone put a minus at the beginning of a line?
- Yeah, that's just plain silly.
- It must be an edge case.
- Unless they really mean a list, of course.
- Yeah, or signature, but it's so rare to sign your contributions on a wiki.
- Yup, you use list with mutiple levels of nesting much more often.

A counterexample is the use of bold as the fist markup in a list item, just take a look at the formatting on this example page [[]]. This is quite common and therefore not an edge case.

Programmers tend to give users all the options a user could possibly want, making it really difficult for a user to actually find what they want.  Extensive menus of word processors are good examples of this.

//What is the most important thing to the average computer user? They want their machine to "just work". Why does Google know how to correctly translate a United Parcel Service tracking number, while the actual UPS website requires multiple entries just to get to the point where the tracking number can be entered?//

A two hour podcast that describes edge cases in detail is available at [[|Why Software Sucks]].