I disagree - for me Twitter is more a social network than a "news source". It's hard enough to keep track of my current timeline (I already can't read a backlog of more than 6 hours! Sucks!), I don't even want to imagine how my TL would look like if I'd follow even one major news site.
It could be interesting if we could follow someone only for some hashtags. This would be an interesting way to filter the feed.