I may be in the minority, but I don't understand why most people on twitter wish to consume most tweets. Outside of a synchronous or semi-synchronous (e.g. IRC) conversation, It's pretty hard to say anything worth saying in 140 characters. I hate twitter and I hate tl;dr as a meme. HN as a community tends to encourage longer posts for the same reason; they're more likely to be interesting.

It works better for sharing content, but I don't usually want to see all content that a particular person wants to share. Other mechanisms work better for getting a list of content to consume: RSS offers all the content from a particular source, and sites like HN and reddit show recent content that a particular community finds interesting.

The only thing I see twitter as good for is disseminating facts to a large audience when a non-internet-capable phone is the the only communication tool available. It has served that function a number of times during war, natural disasters and other breakdowns of civil infrastructure. Even so, I'd rather consume someone else's aggregation of the facts rather than track down which users to follow myself and unfollow them after the event is over. That's what reporters (including bloggers) are for.