Professional at the begginning but unprofessional and unethical. A company that uses interview for strategy and tries getting the most out of interviewees skills knowing very well they have no intention of hiring someone.By the second one on one interview an interviewer is usually sure if he wants to proceed with the candidate or not. They will issue you with case studies and try getting the most out of the interviewee on areas of strategy before sending a very disrespectful regret.