"The content of message is intended to be understood by humans."

From the Intellisense documentation for FileNotFoundException in .NET 2.0.

From a usability perspective, not sure I'd want to see the text of any exception leak to the end user. Certainly not very often. Even if I wrote an end to end application, I'd handle the exception and display it in a more friendly easy to digest manner (and even better, try to prevent it from ever becoming a problem).