Why are Exceptions said to be so bad for Input Validation?

Question

I understand that \"Exceptions are for exceptional cases\" [a], but besides just being repeated over and over again, I\'ve never found an actual reason for this fact.

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Answer 1

1. Maintainability - Exceptions create odd code paths, not unlike GOTOs.
2. Ease of Use (for other classes) - Other classes can trust that exceptions raised from your user input class are actual errors
3. Performance - In most languages, an exception incurs a performance and memory usage penalty.
4. Semantics - The meaning of words does matter. Bad input is not "exceptional".