Basing on what I can learn here*
http://www.youtube.com/watch?v=b83dIs7S4Ug @ 8:00 smaller sub pixels would collect less light, so they would be less effective in displaying decently saturated colours.
Since these phisical limits I'm having serious difficulties in understanding where to find Triton's appeal for ebook readers, at present.
*
despite the guy knows nothing about educational needs and practices 