Amazon.com on Tuesday announced a joint partnership with Berkshire Hathaway and JP Morgan to create an independent health-care company for their employees, putting an end to months of speculation that the technology giant was eyeing a foray into the medical industry. It’s yet another endeavor for the company, which last year spent $13.7 billion to enter the grocery business with its acquisition of Whole Foods Market. (Jeffrey P. Bezos, the founder and chief executive of Amazon, also owns The Washington Post.)[Amazon, Berkshire Hathaway and JP Morgan Chase join forces to tackle employees’ health-care costs]But as the online retailer expands into new industries — cloud computing, drones, tech gadgets, moviemaking and now health care — some privacy experts say the company’s increasingly dominant role in our lives raises concerns about how personal data is collected and used. What happens, for example, when a company that has access to our weekly shopping lists, eating habits and in-home Alexa-based assistants also becomes involved in our medical care?