But an astonishing number of the pages we visit to learn about private health concerns—confidentially, we assume—are tracking our queries, sending the sensitive data to third party corporations, even shipping the information directly to the same brokers who monitor our credit scores. It's happening for profit, for an "improved user experience," and because developers have flocked to "free" plugins and tools provided by data-vacuuming companies.

In April 2014, Tim Libert, a researcher at the University of Pennsylvania, custom-built software called webXray to analyze the top 50 search results for nearly 2,000 common diseases (over 80,000 pages total). He found the results startling: a full 91 percent of the pages made what are known as third-party requests to outside companies. That means when you search for "cold sores," for instance, and click the highly ranked "Cold Sores Topic Overview WebMD" link, the website is passing your request for information about the disease along to one or more (and often many, many more) other corporations. 

According to Libert's research, which is published in the the Communications of the ACM, about 70 percent of the time, the data transmitted "contained information exposing specific conditions, treatments, and diseases." That, he says, is "potentially putting user privacy at risk." And it means you'll probably want to think twice before looking up medical information on the internet.