the iphone has a browser, and most sites have mobile versions, or are more and more being designed with these in mind (a case of point being the recent disasterous relaunch of the bbc news site itself). So what exactly does an 'app' do in these cases?
if this is so, why can't we (900/810/800) users access these sites/streams/whatever that the 'app' is accessing?
Because there is no guarantee that an iPhone-oriented HTML5 site will render equally well on MeeGo (note that under MeeGo I don't necessarily mean just handhelds). Add to this the dance around Flash, WebM/H264 and it's Internet Explorer all over again.
Certainly, but it's a step back. It has been a long and arduous fight (and not even completely over) to get the web to be resolution/aspect/DPI independent. Instead of truly addressing the problem of new form factors, we are simply discarding what has been learned with the web and going back to square 1, brute forcing the problem with specialized versions - a path that cannot be pushed on the long term.