Banner Health hired Executive Health Resources to fight back against Medicare and UnitedHealthcare when they deny claims or pay bills for less than what Banner thinks it is owed. But Banner executives began to worry about EHR's independence when the firm was acquired in 2010 by UnitedHealth Group. As insurers eager to add revenue streams convert themselves into diversified health-services companies, they often buy traditional business adversaries, including physician groups and hospital consultants such as EHR. They're also buying technology companies and research firms that serve medical-care providers, raising questions not only about independence but about the privacy of patient information.