Today I was looking for an item on online stores and was surprised it was out of stocks on many online stores. Some of them had 'Out of stock' instead of the price. 
They all shared the same annoying feature. How do I know when they have it back in stock? I had to send each one of them the same question. I have found this annoying issue on most of the stores. Why can't they have a feature of .. Enter your email address and we'll notify you when it's available again. 
These stores expect me to keep checking their store all the time to see if they get the item in stock?? This is bad user experience.

I hope the DNN shopping cart/e-commerce module developers implement this feature. Just displaying 'Out of Stock' is not good enough. Enable store owners to care more about their customers. This feature helps store owners get repeat customers.