Walls as Security Theater
Interesting essay on walls and their effects:
Walls, then, are built not for security, but for a sense of security. The distinction is important, as those who commission them know very well. What a wall satisfies is not so much a material need as a mental one. Walls protect people not from barbarians, but from anxieties and fears, which can often be more terrible than the worst vandals. In this way, they are built not for those who live outside them, threatening as they may be, but for those who dwell within. In a certain sense, then, what is built is not a wall, but a state of mind.
The essay goes on to talk about the value of walls as security theater.