Fear of the unknown about your own body. Think of how many people would sign up if you sold a service that scoured secret files to "find out what people are say

Fear of the unknown about your own body. Think of how many people would sign up if you sold a service that scoured secret files to "find out what people are saying about you". Forget whether such a service could ever work, just the combination of "unknown" + "about you" is irresistible to a large segment of the population. It's the mother-of-all-clickbait.