Should I be careful who I share my unpublished results with?
In science, just as in most areas of human activity, most people try to behave ethically but some have skewed views of ethics and some are just plain nasty.

Good ways to protect yourself are:


Asking somebody you trust who knows about the ethical character of the person you are looking to contact.
Putting a draft of your work up online, e.g., arXiv, that can clearly provide a time-stamp on your work.