Adi Shamir wrote that the president of his institute says: "It is clear that scientists have been singled out, since I hear that other ‘simple citizen’, do get their visa in a short time." Scientists get more scrutiny? What in the world is going on there?
One of the grad students I know was told he was not allowed to renew his student visa unless he stopped working on computer security. He had to switch advisers and the school had to swear that he would not be allowed to continue his previous work.