Phone metadata more revealing than expected (Stanford research)

"Volunteers who chose to participate allowed researchers access to their calling and texting data, the date and time, and the duration of the call. ... We found that phone metadata is unambiguously sensitive, even in a small population and over a short time window. We were able to infer medical conditions, firearm ownership, and more, using solely phone metadata.... The new results provide a strong, research-based analytical counterweight to the government assertion that metadata is somehow less revelatory than capturing actual call data." - Volunteers in metadata study called gun stores, strip clubs, and more | Ars Technica