Or, in the case of LAX, an entire neighborhood was demolished as LAX expanded. If you look out the window as you take off from LAX, you will see below you the remnants of that old neighborhood. It's really creepy if you drive by that neighborhood because it's all fenced off and there are no houses, but the streets, lights, and palm trees are all obvious signs of a former residential neighborhood with some of the most gorgeous ocean views around.

Here's a story on how it happened. There are some cool links on the bottom, too.