Twitter made an announcement today about stopping abusive accounts and hiding low-quality tweets. I think filtering search results in particular is a very good step in the right direction:
We’re also working on ‘safe search’ which removes Tweets that contain potentially sensitive content and Tweets from blocked and muted accounts from search results. While this type of content will be discoverable if you want to find it, it won’t clutter search results any longer.
As I work on Micro.blog, I’ve tried to be mindful of where users can stumble upon posts that they don’t want to see. Replies is a big one, and I’ll be focusing most of my attention on that. But search, trends, and hashtags are also a problem, because they let anyone’s posts bubble up to a much wider audience. I’m launching Micro.blog without them.
Conversation on Micro.blog