Headings should remain at visible size when zoomed out. The idea is to get an overview of a document by zooming out, click the spot and drop back in, but the headings become too small to be of any use in navigating. My kludge is to make them big, like 50 pt, so they're visible when zoomed out, but when you zoom back in, humongousity ensues.
This is a general zooming interface idea: the things you navigate by should remain visible when zoomed out.
