High Stakes Issues
… fear of individual exposure when participating in political debates over high-stakes issues can dissuade people from taking part. That’s why the Supreme Court ruled in 1958 that membership lists of groups have strong First Amendment protection. Telephone records, especially complete records collected over many years, are even more invasive than membership lists, since they show casual or repeated inquiries as well as full membership.
— Electronic Frontier Foundation legal director Cindy Cohn