Some writers are way too paranoid.
I agree, but I also understand where the hysteria and paranoia comes from. I am a very competitive person within my interests that offer competition within in its means. I've seen insecure people get really concerned that someone will steal their ideas before they have had time to finish their project. Are there really people out there that would steal ideas for a book? Sure. But the chances of these few finding us is so slim that to worry about it is...well...paranoia!
I can understand the fear of someone stealing words from an excerpt online, but not with the idea itself. Even if someone did use the idea for themself, the execution wouldn't be the same. It's the writing that makes the book. There are many stories based on the same fairy tale, but each are vastly different. And, as you said, the chances of those unethical people finding you is incredibly thin.