Typically it's based on self reported domain expertise and general hiring interests that you express to the recruiter - to check your competence in what you claim your competence is. But overall the hiring process is slowly changing and now you're more likely to be targeting more specific area of the company, and then your interviewers have a high chance to later be ones during team matching calls. When I started interviewing, I went for a year of ~2 interviews a week and never saw anyone I'd know on the list of other interviewers. Now it's getting more and more likely (other interviewers for example also work at Research and we are interviewing candidates targeting Research).