It is not whether you need a database or not. It is "how configurable/dynamic things should be". More configurability usually means more power to your users and

It is not whether you need a database or not. It is "how configurable/dynamic things should be". More configurability usually means more power to your users and more pain to maintain the software. So I usually go to the least amount of configurability and then add things when required. The same goes for abstractions (you often need more of them when things becomes more configurable)