No, there is nothing illegal about that at all (at least in the United States, as a general principle of law) but that appears to be a very common misconception

No, there is nothing illegal about that at all (at least in the United States, as a general principle of law) but that appears to be a very common misconception here on Hacker News. (Thank you for saying "correct me if I'm wrong," indicating that you desire to learn something here on Hacker News.) In general, an employer has somewhat of a DUTY to hire carefully, especially if the people the employer hires will have access to personal information of other persons, or to dangerous instrumentalities, or could otherwise cause criminal or civil harm on the job. Employers who are well advised about the law of "negligent hiring and supervision" and the legal exposure that companies can have from a careless or evil employee take care to check references, to ask the references for back references, and to include a job applicant authorization for an appropriate background check (usually contingent on a firm job offer, but also as a condition for continued employment) as part of the hiring process. Employers are allowed to find out, and are EXPECTED to find out, reliable information about the public workplace behavior of the people they hire. Thinking that the job applicant can control the information flow in the entire process by how the applicant fills out a resume or an application form is one of the biggest misconceptions nonlawyers here on Hacker News have about employment law (again, at least in the United States, the jurisdiction I know best). To the best of my knowledge, there has never been, and could never be, a successful lawsuit by a rejected job applicant if an employer checked back references (for example) and found out something about the applicant's previous PUBLIC, WORKPLACE behavior that suggests that the applicant would be a bad fit for the new job.