Answer:
Expert William McGeveran in paragraphs 17 through 21 and paragraphs 27 and 28 develops the central idea that social media sites are not private places by providing information on the legal framework that governs social media sites and how user data is collected and used. He explains that social media companies are not considered "publishers" under the law, meaning they are not held liable for user-generated content. He also notes that these companies have broad terms of service agreements that allow them to collect and use user data for various purposes, such as targeted advertising. Additionally, he cites examples of how user data has been used in ways that many people would consider invasive, such as political campaigns using data to target potential voters. Together, this information demonstrates that social media sites are not private places and that users should be aware of the legal and practical implications of sharing their information on these platforms.