Internet promoting pseudo-epidemics?

You see the signs promoting cancer screening nearly everywhere you go these days -- airports, bus stations and online. The ads promote cancer screening as a form of preventive medicine, and almost always refer you to an Internet site, where you can learn more about screening, and even register for screening for brain, heart or lung cancer -- and other dreaded maladies -- online. No doctor's appointment needed. Just sign-up and get the test results yourself from the lab.