I believe the solution to this problem isn't tiny frameworks, it's better tools and/or languages.

Closure Compiler and GWT do a great job of stripping dead code. Cappuccino has a tool I wrote that attempts to analyze your application and remove unused files from the final bundle of code. It could do a lot better though.

One thing these tools have in common is static typing vastly improves their ability to remove unused code. Perhaps JavaScript and other very dynamic languages aren't ideal for large web applications built with large frameworks.

I like the idea of optional static typing. For example, a language in which you can rapidly prototype without paying close attention to strict type rules, but later you can "solidify" your code by enabling static typing. Is anyone aware of a language like that?

Edit: now that I think about it, that's basically what Closure Compiler is