Remember, you read it here first

The American Cancer Society finally admits that they have been overhyping the benefits and underplaying the adverse effects of breast and prostate cancer screening.

"We don’t want people to panic,” said Dr. Otis Brawley, chief medical officer of the cancer society. “But I’m admitting that American medicine has overpromised when it comes to screening. The advantages to screening have been exaggerated.”

Abstract of the JAMA article is here. Since you are too low-borne and no account to read it, I will summarize for you. When you start widespread screening, you will, obviously, have a sudden jump in the incidence rate of cancer, because you're detecting more of it. What you want to happen is that after time, the incidence of serious disease and death goes down, because early detection has prevented many cancers from becoming serious.

What has actually happened is that the incidence of prostate and breast cancer have doubled; but the incidence of serious disease and death has declined little for both types of cancers, perhaps not at all due to screening. Periodic screening may be good at detecting early stage lesions that will never develop into meaningful disease before the person dies of something else; but tend not to find more dangerous cancers early enough to make much of a difference. And that appears to be what is happening. A large burden of morbidity and treatment for innocuous lesions that would never have caused a problem, in exchange for a very small reduction in the rate of serious disease and death, if any.

Mass screening would be much more useful if we could distinguish the dangerous lesions from ones that just bear watching, but as of now, we really can't. The shameful truth is, however, that without having good evidence that screening really does save lives or that the benefits outweigh the costs, the ACS and disease-specific organizations have undertaken mass campaigns over decades to try to get everyone to be screened. Of course there is money to be made at every stage, from radiography to lab to surgery and chemotherapy. Is that why they jumped the gun on the evidence? Who would think such a thing.

And while we're on the subject of what you read here first:

As I and others have been saying for some time now, the influenza surveillance data which has been used to describe the novel H1N1 pandemic is based, not on actual confirmed cases, but merely on the number of people who present with flu-like illnesses. For some reason, the public has been told to assume that most of these are in fact cases of novel H1N1 influenza, but that has not been established. CBS News now reports that the overwhelming majority of people who have been tested did not have novel H1N1 influenza, or even, in most cases, have any form of flu. Hmm.

Update: Kathy's comment reminds me that I should clarify something. The new position from the American Cancer Society refers only to mass screening of the general population. If you are at high risk -- for example, because you have a "first order relative" (parent or sibling) who has had breast cancer, especially at a relatively early age, your cost/benefit profile is very different, and mammography makes much more sense for you. I'm not here to give individual medical advice, but to talk about broad policy. You should make your own informed decisions, hopefully in consultation with your physician.