Aliza Rosen, writing at the Twitter Blog:
We want every person around the world to easily express themselves on Twitter, so we’re doing something new: we’re going to try out a longer limit, 280 characters, in languages impacted by cramming.
Our research shows us that the character limit is a major cause of frustration for people Tweeting in English.
I have a very simple solution to this problem. Avoid Twitter’s limitations by writing at your own web. There’s no limit there, nor is there an “emotional attachment to 140 characters” that you “feel.”