FarmVille players rejoice! You can now upgrade your storage through a new feature called
barn raising:

To expand the capacity of your buildings, simply click on the building of interest and you will notice a new option - "expand storage". By clicking that, the following menu will pop up:

Note that in the picture above I had already started the barn raising process. Here's how it works:

In other words, when you click "expand", you will be able to post a help request to your wall. Your friends will see this update in their news feed and be able to help you out by clicking on a link:

If 10 people help you out, your building will be upgraded to an improved storage capacity. As you may have noted in the picture above, the Tool Shed you can buy with coins can be upgraded to store 7 items in. As a result with the addition of this feature, there is a way to get a decent amount of storage without spending any farm cash. Helping out a neighbor gives the helper 100 coins as a reward.
Although it says the price for an instant upgrade decreases with each person that helps you out, the cost for upgraded the tool shed from 2 storage spaces to 7 storage spaces still costs 10 Farm Cash when 9 out of 10 friends have helped you out.
Once 10 people help you out, your building will be instantly upgraded:

As you can see, my "Tool Shed" has become a "Big Shed" and now holds 7 items instead of 2. With a third and final upgrade, a simple tool shed will hold 14 items. Not bad for an item that only costs 14,000 coins!
There is no cool down at the moment on upgrading buildings. As soon as my tool shed became a big shed, I was immediately able to ask for help on expanding it again. Even more important,
upgraded buildings do not increase in size, so the storage is increased but there is no additional farm space used up by this expansion.
The more exciting thing is that Dairy Farms and Chicken Coops will be added to this expansion system soon. This will make these buildings much more valuable and make it much more profitable to have multiple dairy farms on a single farm. Based on the massive storage increase as a result of upgrading the Tool Shed, it would not surprise me if an upgraded chicken coop or dairy farm each held 50 animals.
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Lop-Eared BunnyAlong with this update came the addition of a new cash-only animal:

The Lop-Eared Bunny produces 90 coins every 2 days and costs 9 Farm Cash.

FarmVille Storage Expansion and Barn Raising; Guide