In the same vein as this question, but not entirely the same:
When designing a library to be consumed by someone else, is it best to split it into as many functional unit assemblies as would make sense, or should something like toplevel namespaces be a good guide as to how to split it up, or should it all go into one huge assembly?
I'm particularly interested in .NET for the purposes of this question, but answers regarding other languages/frameworks are more than welcome too.