When a place gets crowded enough to require ID's, social collapse is not far away. It is time to go elsewhere. The best thing about space travel is that it made possible to go elsewhere.
The second best thing about space travel is that the distances involved make war very difficult, usually impractical, and almost always unnecessary. This is probably a loss for most people, since war is our race's most popular diversion, one which gives purpose and color to dull and stupid lives.But it is a great boon to the intelligent man who fights only when he must - and never for sport.
Robert A. Heinlein, Time Enough for Love (1973)