From the "Just My 2-Cents" Department...

What Twitter needs is (like YouTube) a Thumbs-down icon. Without one, if you disagree with a tweet, the only option is to tell someone off, often angrily. And that's gets responded to. And things blow up. But a Thumbs-down icon could be clicked, and you move on. It won't solve anything, there still would be a lot of anger vented, but I think it would lessen some of it and help.

Facebook could use that, too, though Twitter mostly because with its character limit it seem more centered on quick, snap replies.