Every time my father sends portrait photos taken on his iPhone to someone in the family that doesn't have an iPhone (eg. Android and Windows Phone 7 devices), they come through landscape. When we try to turn the phone to see the photos correctly, our devices rotate the photos, making it impossible to actually view them the correct way up. ARGH!
Anyway, it seems to be that the iPhone stores all photos landscape, and if they were taken portrait, this is stored in the EXIF data, which the iPhone handles correctly... However, it seems very few other devices handle this (including most web browsers).
What I don't understand is why EXIF stores orientation. Why doesn't the iPhone just rotate the picture so it's always upright? What advantage could the current method have? (and is this really a good enough reason to break compatibility with so many photo viewers so badly?!).