That is an interesting idea. If people think it would actually help internationally I can look into what Camtasia studio offers for something like that. Though my version is 3 behind the current release, so I don't know how easy subtitles can be added and changed. Though this wouldn't happen in anycase, until the videos are done the normal way.
Yes, I do like the idea of subtitles. It's especially good if the subtitles can be separate from the video since that would allow others to add their own subtitles, possibly in a bunch of different languages.
Someone posted a link to a photoshop effect in the last week or so and the video showed a way of preserving the pixel resolution of some objects in a scene while resizing the image. That video had subtitles and below the video was a "table of contents" that showed a timestamp and the text of the subtitle at that timestamp.
If such a thing could be added without too much effort, it would be a great boon! Your video tutorials would become searchable by Google, et al, since the subtitle text would be on the page!