I have seen recruiters; Phone all the sequential numbers in the office to try and find anyone with a similar skill set. Contact all my referees and supervisor

I have seen recruiters; Phone all the sequential numbers in the office to try and find anyone with a similar skill set. Contact all my referees and supervisors trying to hunt them. Ask me if I know/knew "John" who worked with me on a previous project. Send me on an interview just to test out a potential client, so they can get my feedback. And they always ask "Where have you interviewed recently?".