Legal guidelines about how information about people can be collected from social media Web sites often depend on who is doing the investigation. Law enforcement or parties in lawsuits have different rules and expectations compared to businesses doing background checks on job applicants or a private citizen undertaking a personal investigation. That said, this chapter lays out the current legal landscape. There are two core legal issues that come up in this area: a person's right to privacy and the investigator violating a site's terms of service (TOS). We will look at those areas individually along with a list of common investigative techniques that have not seen any legal challenge.