Catchy jingles? Splashy videos? Multi-million-dollar public education campaigns? For the 16 states and the District of Columbia that have opted to run their own online health insurance marketplaces, these are among the tools being used to make sure residents know the exchanges will be open for business Oct. 1. (Other states will either operate exchanges in partnership with the federal government, or will turn the task completely over to it.) These marketplaces, which were created as part of the health law, are key to the overhaul's goal of expanding coverage to millions of uninsured people. But for that to happen, those same people have to use them.