So what does this mean for Twitter? IMHO their continued growth and longterm utility will be based upon filters - both explicit user controls (such as groups) and implicit prioritization (order by "interesting" not chronology). If Twitter doesn't do it, certainly the ecosystem of developer apps will nail it. Ev has talked about designing with constraints - he famously fantasized about a social network which limits you to only 10 friends. Well, that's one way to keep high signal, low noise. Another is to treat data intelligently, and my bet is that's the way Twitter (or the ecosystem) will go.
Here's some of the filters i'd find potentially useful:
Explicit (ie dependent upon me)
- deprecate/mute tweets containing kw= or #=
- Google Reader integration - if i already subscribe to someone's feed, i don't also need to see their tweet announcing they just posted
- sort by interestingness (based upon # of retweets, how often i tweet @ that person, etc)
- collapse dupes - turn retweets among those i'm following into a single group
- conversation view a la TweetTree