I've always been a proponent of displaying new lines in tweets (especially because sometimes I tweet short poems). Twitter seem to have finally done that, but without putting much thought at it - you can now have tweets that span the entire screen.
What I write a while ago (http://web.bozho.net/?p=262) was:
"someone may enter 20 new lines and thus break the timelines of their followers. That’s an easy thing to fix – just don’t display more than 2 consecutive new lines, and also limit the total number of new lines per tweet to, say 5 or 6."
I post this on HN, so that (in case it gets upvoted), it puts some sense into twitter product designers.