I'd really love to see Twitter implement something approximating the reverse of Google+ style circles. Sometimes people follow me because I'm a developer, but I feel guilty when I post stream-of-consciousness nonsense into their feed. It would be great if I could separate that out - subscribe to @me/dev and/or @me/nonsense.
Of course, such complexity might put off new users, which is the problem they already have.
Of course, such complexity might put off new users, which is the problem they already have.