Thanks mcherm, this is the best counter-argument to the WTFPL I read all day.
I am myself extremely curious about what would happen in these two circumstances:
1) someone uses my work and then sues me for copyright infringment;
2) my work harms people.
Unfortunately, the legal system is intentionally designed in such a way that you can't easily satisfy your idle curiosity on that subject. You can ask a lawyer, who'll give you their best guess, but the only way to tell for sure is to get sued: there has to (with a few specialized exceptions) be an actual controversy before a court considers a question. This was (in programmer language) designed intentionally to protect scarce resources (court time) from certain kinds of denial-of-service attacks.