Where's the nearest cash machine? http://tnaflix.in.net/ tnaflix Officially a Medicare experiment, ACOs are proliferating. In the three years since Obamacare passed, hospitals, medical groups and other organizations nationwide have formed 488 ACOs, says Andrew Croshaw, managing director of Leavitt Partners, a health care consultancy that follows ACO development. "There are a lot of experiments happening in the commercial sector, too," he notes. Medicare contracts with 250 ACOs, covering more than 4 million beneficiaries; the rest of the ACOs operate under private health insurance deals covering 14 million to 23 million more people.