I am looking for Magento retailers that allow backorders on their website so I can compare the user experience with what we are currently doing today. We are on Community v.`1.9. Thanks in advance for any websites you can point me towards!
I don't have any specific example from a Magento merchant but I recommend you to review the extensions from Magento Connect that provide that custom feature.
By doing that, you will be able to see the custom implementation for that feature from the different module vendors.
Here is one example: https://amasty.com/magento-pre-order.html