Looking at this more from the non-technical end user perspective, my rule for error messages is that they should always be actionable. If the viewer is the developer, then technical details are important. But if the viewer is an end user/consumer, they don't necessarily need to know exactly what happened, but they do need to know what to do.

For an average end user...

* If the hard disk is full, that's easy to convey and easy to suggest a fix.

* If a hardware fault occurs on activating a device, suggest they try again and contact support if the problem persists.

* If an unhandled exception occurs, all they need to know is that something very unexpected happened, and they should contact support - they don't need to see a stack trace and error message.