Serializing complex documents that have many optional lists results in the explicit serialization of an empty collection (i.e. ), which is a waste of space, and makes indexes unnecessarily large and clumpy.
I have littered my classes with a bunch of "ShouldSerializeXXX" methods, which does resolve the issue, at the cost of some additional typing. But I think it would be useful to implement this as a convention. That way, it could be established as the default, and would provide a more robust way of implementing this option globally (for all collection or IEnumerable types).
It may be possible to do currently, but I haven't figured out how to do it. I suspect that this option might by widely useful.