When it's time for a new line of work...
Sometimes, it can be a little difficult to tell when you should be investigating a new line of work, but in the case of this developer, the case seems very clear.
Boing Boing and Slashdot point out this story of a Macintosh software developer who is so fed up with the pirating of his software that he programmed in a "nuclear" defense. Instead of simply disabling the software when a pirated serial number is used, the developer included code that will delete a user's home directory (i.e. all your documents, pictures, music, preferences and settings) when it detects certain, pirated, serial numbers.
I do not support software piracy, but it seems clear that this developer has not only destroyed their own business, but may have opened themselves to legal action, up to and including felony charges, if this software bomb is ever activated.
Each business has its issues and software piracy is certainly a concern of any software developer, yet this action is clearly self-destructive. No one how is aware of this issue will ever install another piece of software from this developer, out of fear of what might happen.
You shouldn't wait for self-destructive behavior such as this to indicate when it is time to find a new job or career. Yet, we often find signs of such career suicide in our own lives. Workers who not only do worse and worse at their job over time, but also start actively sabotaging their companies and fellow employees. The truth is, you damage yourself far more than anyone else. In the end the damage to your own life could be so severe that you may have trouble finding any work at all.
If you are unsatisfied with your career, direct your energies to finding something new, not in destroying everything you have created.