The plan was to use anonymized data from both Facebook and healthcare providers and with hashing, match them up. Facebook information about a user like their age, whether they're married and have kids, what language they speak primarily and how often they engage with friends or family online would be matched to health data, such as age, medical conditions, prescribed medications and how often they visit the doctor. Researchers would then look to see if the added social media information might help improve patient care. For example, finding a patient doesn't have family or friends nearby might be found to necessitate a nurse checking on that patient at home following a surgery, says CNBC.

"The medical industry has long understood that there are general health benefits to having a close-knit circle of family and friends. But deeper research into this link is needed to help medical professionals develop specific treatment and intervention plans that take social connection into account," Facebook said in a statement. It added that last month, it decided to temporarily halt the project "so we can focus on other important work, including doing a better job of protecting people's data and being clearer with them about how that data is used in our products and services."

Which was a smart move. The company announced yesterday that as many as 87 million Facebook users' data were improperly obtained by political firm Cambridge Analytica, many more than the 50 million affected users initially reported. With so many now wondering whether they should trust Facebook with their data, it would be very hard to get people on board with the company having access to their medical histories, even if they're anonymized. According to CNBC's sources, patient consent did not come up in early discussions of the project. Facebook made clear that it has not received any medical data, a point that the American College of Cardiology reiterated.