Friend of mine worked for a Fortune 500 company that was playing an interesting game: They would open a job req with a narrow set of qualifications. If a US citizen showed up and matched the qualifications, they would hire them, then eliminate their position 6 months later. But then they'd slightly change the job qualifications to exclude that person, and try again. (It seemed like it was part of some lobbying effort to say "Look how many job openings we can't fill!")