its a ancient Chinese "remedy" but sense when was validity determined by age and country of origin?
in terms of modern knowledge theres nothing to support the methodology of cupping. there has never been any observed "chi lines" in the body, and everything we have observed in the recent centuries tells us that the causes of medical problems is not simply the "blocking of chi" but injury, infection, genetic deformity, malnutrition, non of these conditions can be relieved by creating a vacuum on the skin.
more info http://www.skepdic.com/cupping.html