System would be good or bad

Let's say we live in a world that has a good screening test for every known disease. Let's say they were also inexpensive and you could order them online anonymously. Since we're daydreaming here, let's also say you could complete the test privately at home and relatively easily. Do you think this system would be good or bad--and why? Would you want to know your results for a serious disease? Why might be a problem you foresee with such a system? In your responses, please write at least 150 words with 1 reference