After tweeting that I really want all of my “readers” (mail, rss, twitter, etc) to allow me to sort items with the newest on the bottom, a friend asked “why.”
The answer is that I read from the top down. Since tweets and other items tend to build on each other, you want to read the oldest first, then build up to the most recent. Given this “I’ll read them all in order” approach, my eyes can just flow straight down if the oldest is at the top and the most recent is at the bottom.
Otherwise my eyes have to read the bottom item (moving a small amount down) then jump up tho the next item and read a little down, then jump up. I keep doing this for a long time.
Newest at the bottom solves this problem.