We've redone our product catalog for a website using a NoSQL solution ( not MongoDB, but we did look at it). Our products are in multiple different categories, and have vastly differently attributes depending on categories. NoSQL solutions are perfect of this. As you point out it's a simply alternative/solution to deploying an EAV model.
I've only seen EAV used in one system, Magento, but was a disaster. It's complex and slow to the point that very product in stored both in the EAV model and as a "flattened product".
For systems dealing with sales and economy in general I would almost alway pick a RBDMS, it's seems a much more natural fit. The ability to do ad-hoc queries in SQL, rather that map-reduce is a huge advantage.
I've only seen EAV used in one system, Magento, but was a disaster. It's complex and slow to the point that very product in stored both in the EAV model and as a "flattened product".
For systems dealing with sales and economy in general I would almost alway pick a RBDMS, it's seems a much more natural fit. The ability to do ad-hoc queries in SQL, rather that map-reduce is a huge advantage.