We were pleased to read the recent article by Greaves et al1 outlining new methodological techniques to analyse patients’ online ratings of care. We agree with the authors that social media websites not only represent a wealth of first-hand patient experiences with health and health care but also have largely remained untapped by biomedical researchers, especially to gain new insights into how to improve clinical care. We concur that ‘big data’ techniques, such as machine learning and natural language processing, can be extremely powerful to synthesise the large amount of textual data on these sites.

However, …