Some people can't keep chickens because of city or HOA regulations or because of space requirements, but they would like to.
A good option for those people might be Coturnix quail. Quail eggs are especially delicious, and so are quail (if you can stomach cleaning them, it is pretty easy). These birds take up a very little space and are extremely quiet. Eggs are about 1/3 the size of chicken eggs. It's a really good way to sustainably have top quality eggs in a suburban setting (and possibly even indoors).
We keep chickens and wouldn't go back to store bought eggs even if they were 50 cents a dozen. Not the same egg. It is a little bit of work, but not bad once you are set up. It helps that we are also avid gardeners and so chickens get a lot of waste and greens (which also makes much nicer eggs).