I keep trying to explain what bothers me about FRBR, and in particular about WEMI. I've recently thought about it it with this image of a cake. I know this is a flawed analogy, but it works for me on some level. It goes like this:
When you make a cake, you have a number of ingredients:
When you mix them together to make a cake you don't get this:
You get this:
My point here, in case it isn't clear, is that the purpose of creating a bibliographic description using a number of different entities is to... well, to create a bibliographic description; something that as a whole has meaning. You can create it from individual "ingredients," like information about a Work and an Expression, but those do not need to remain separate entities in your final product; instead, that information can become part of your whole.
I know that people like the idea of a distributed bibliographic description with a single Work entity that links to many Expressions that then link to many Manifestations, etc., and that could be the underlying structure of ones data store. But just because there are Work entities (eggs) doesn't mean that our metadata keeps the Work entity "intact." In fact, our systems may use only a portion of the Work entity, and may use bits of it at different times in different contexts.
Leaving poorly-drawn analogies aside, creating our data as sets (or "graphs") of triples should give us maximum flexibility. One thing this means is that even a partial description is valid. Thus a full library catalog record and an abbreviated citation are both valid representations of a resource. They should connect to the larger linked data information space through any of the statements they contain, regardless of the structure of their graphs. And it is my guess that many bibliographic descriptions will be simple graphs with a single RDF subject (that means a single bibliographic resource). The highly structured bibliographic universe of FRBR will be a minority case, and the FRBR entities, like our eggs and sugar and flour, will be useful ingredients that disappear into actual creations.