I would like to add a little bit of personal opionion on the OODB topic.

The concept of an Object-Oriented Database just seems wacky  to me. Objects imply action. If you're thinking in terms of Object-Oriented programming, the really important stuff is the behavior of the objects. The data storage is irrelevant. In reality, a relational DBMS is the perfect data store for an OO system. There isn't anything the relational model can not handle for OO data storage. The only thing it can not handle is the behavior/methods/operations/pick-your-term. And by all rights it has no business performing actions on the data since that is clearly business logic.

I worked with another DBA that did some considerable research on OODB's and his conclusion (Which I expected it to be in the first place) was that they are immature constructs for developers that are too lazy to build a code generation engine to develop the code between the data and the business logic. (Quick plig for my favorite code generator - CodeSmith)