Years of sub-par screens and using the pixels as units of length made people think that higher resolution means smaller elements. This is not true. Higher resolution means more clarity with similarly sized elements. 300dpi has been the low barrier for printed material since a long time ago. It's time screens get up to par. Are all business cards hard to read? They are still 600dpi though. Increasing resolution without increasing screen size becomes pointless only well north of 300ppi for handheld devices (including books)

Now when viewing distance increases, that changes.
If you want to read more about that http://play.qwazix.com/grog/?p=456