Colin, first, thanks for your long, detailled answers! Just a short reply: On 09.11.2011 11:56, Colin Guthrie wrote: > Now consider two users on an accessible system: One is visually impaired > the other is not - at the same time. OK, but that's really an unrealistic case now. The blind guy needs the sound output, so likely he doesn't have somebody else working on the same machine at the same time. More realistic is: An average couple, he is a unix geek. He has a notebook and a tablet. The notebook is connected to speakers, running mpd for music. Tablet is running mpdroid and controls the mpd. The notebook has 2 users (but never at the same time), so the geek doesn't want to log in to any particular account just to listen music, but wants mpd to work irregardless of the logged-in user. There's no conflict, because if the music disturbs her, she'll just turn around and tell him to stop. Which, I think, will be true for almost all cases where you have 2 humans around the same computer at the same time.
