They give you chickens. White eggs give white chickens, brown eggs gives brown chickens and so on. Sometimes they turn into other gifts also such as a picnic set.
Turtles in farmville give "turtle eggs" when ready.
eggs
nowhere they get sold instantly.
NO they don't
It gives you 80 coins after collecting their eggs.
On FarmVille it says consumables, but they are not actually consumable, they are things like Milk and Eggs, which are only consumable in real life, not in the game.
Mystery eggs gives item bonuses depending on what kind or color the egg is.
by harvesting your trees. They can also be found in White Mystery Eggs.
In FarmVille, the eggs will last forever in the coop. They will never go bad the way crops wither.
you can ask your friends for them, click on your basket and use the ask for eggs feature. If your neighbors are also your friends posts will pop up occasionally with free eggs to claim.
I can't say it's stealing but in the new feature of feeding chickens in Farmville, your friends will have the chance to find some eggs in your chicken coop and share it to others. Well you can still harvest your chicken coop and still get the chance to find some eggs and also feed the chickens of your friends and also find some eggs in theirs.
When one of these eggs is opened, it gives an "item". Whether it's a special item or not is the opinion of the person opening it. I use 6 as decorations!