How many features are built-in to a framework or library that your app doesn’t need yet (and may never need)? How much can you hold back from the package you send to the web? How dependent are these modules and bits of code on one another? To me, that sounds like a lot of analysis up front to pick apart a tool before I even write a single line of code to be truly productive. It is also the antithesis of Progressive Enhancement, which strives to start with the bare minimum necessary to make it work and build up from there.