Wow, I never knew someone would use EAV so extensively! Usually the only time we employ such a scenario is when we have a need for "Customer-Defined Fields" (CDFs as opposed to UDFs). These are not fields we would know about ahead of time, nor could we predict what a Customer wants. Obviously we attempt to guide them to use any existing fields "correctly" because (as we all know) every Customer uses different terminology for the same things. Lastly, once we notice multiple Customers using the same "Custom-Defined Fields", we "promote" those to real fields and standardize everyone at the same time.

The idea (I believe) of EAVs is to allow flexibility in the short-term, while at the same time learning about what the audience of the system needs, and then promoting those needs to real models as trends are noticed.