Continuations as UI Elements

Haystack is a "universal information client" -- a program for integrating all the data that typical users work with (email, websites, rss feeds, etc). It has an interesting feature that I haven't seen in GUIs before: it supports "UI continuations" (look about halfway down the page). Visually, these things look like dialogs with a button that the user can click to complete the operation. Functionally, they're first class objects that can be bookmarked for completion later, or even executed multiple times.

This is similar to using continuations to simplify web programming, but it seems like a different enough application to be worth mentioning.

This, combined with Naked Objects, makes me wonder whether users might one day work directly with concepts that are currently exclusively the domain of programmers. Perhaps application programming as we currently know it will one day be viewed as excessively primitive and timid ("Let the user work with data directly? But they'll mess it up!").

Or from a different perspective, maybe theoretical computer science is really the art of discovering useful user interface idioms. Any guesses as to what the UI equivalent of a monad is? ;)