I work in a laboratory staffed by scientists from all over the world. Many of them who are not U.S. citizens are allowed there only because they have applied for and received visas. These agreements allow their holders to enter into our country and stay for extended periods of time. It is critical that folks know exactly when their visas are set to expire so that they can either reapply for new visas to extend their stays or return to their home countries. Every now and then folks run into problems extending their visas even if they are employees of the laboratory. In such cases, they must immediately leave the country until their paperwork is in order. As there is a significant level of bureaucracy involved, sometimes they must leave the country for several months until they are legally able to return. This can be a real hardship, especially as many no longer have places to stay in their "home" countries.
A colleague of mine recently ran into visa problems. He was alerted to this when he recieved a very serious letter from the U.S. government that his visa had been expired for more than 5 months and he had 2 weeks to either leave the country or he would be arrested. The problem is that my colleague had no notion that his visa had expired. In fact, his official paperwork clearly stated that his visa was not set to expire for another six months. When he finally got to the bottom of his situation, he found out that the end date of his visa had changed when he renewed his passport earlier in the year. It appeared that this change occurred due to some computer glitch that should not have occurred, and nothing in the system alerted him to the change until he was on the verge of arrest.
The disruption to this man's life is severe and he was forced to immediately leave the U.S. until he could be granted a new visa. However, the U.S. government has already indicated to him that his visa application may not be so quickly approved as his record indicates that he was a violator of U.S. law with his previous visa. While my colleague is mostly likely good and screwed, the good news in all of this is that our bureaucratic system with its full complement of red tape is fully functional.