It's dying because they didn't manage the tweet-storm dynamic. Journalists love it -- it means they don't need to leave the office and find actual news stories to report -- but to the ordinary public it's a platform for expression that might as well have "DANGER: LANDMINES" signs posted all around it.
Come and hear angry people ranting at the internet!
Rants and tweet-storms get lots of views, lots of clicks. But they are not necessarily what most people want to see. Most people are not on Twitter most of the time. And for most people, their primary exposure to Twitter is "oh look, there's yet another news story about a "public backlash", with a selection of angry tweets embedded in the article".
This is certainly a big turn-off for me. Why should I care about a platform apparently tailored for self-promoting celebrity gossip and low-content, high-drama flamewars?
Beyond that, I've never been able to make any sense out of their threading system; the only way I can figure out what is happening is if someone inside the mess writes an article explaining it and quoting the relevant comments. The actual feeds all seem to be incomprehensible mishmashes of quotes and references to people who aren't present. (I assume there's a view which makes it all hang together if you have an account and actually log in rather than simply browsing, but the fact that I can't really see what's inside the box means I have no motivation to get involved.)
Furthermore, getting too comfortable with a communications medium solely owned and controlled by a single company seems like a recipe for long-term disappointment.
Come and hear angry people ranting at the internet!
Rants and tweet-storms get lots of views, lots of clicks. But they are not necessarily what most people want to see. Most people are not on Twitter most of the time. And for most people, their primary exposure to Twitter is "oh look, there's yet another news story about a "public backlash", with a selection of angry tweets embedded in the article".