Twitter is a ghetto, and most individual tweets are worthless. Yet on any given day there are dozens of really interesting conversations worth following.
Even if the value of individual tweets is fleeting, the value of these conversations and contexts is permanent. The problem is that there's no good way to read through past conversations after the fact. For example, during #sesny today there were ten or fifteen really interesting conversations. But of course for every insightful tweet that contributed something to the conversation, there were twenty that were retweets, spam, nonsense, or just offtopic. That's not so bad when you're reading the new tweets in real time, but trying to grok the conversation later it's completely unbearable.
While twitter as a whole is probably best described as a ghetto, there are a ton of thought-provoking conversations being generated that deserve to be preserved and curated — the same as a museum would do for works of art worth saving for future generations.
As an example of what I mean, check out my lens on the Hacking Education conference that took place the other week. That lens still might not be perfect, but it's infinitely easier to read than scrolling through the 65 pages of mostly-garbage tweets that make up the official #hackedu twitter search.
Every event needs a twitter hashtag, and every hashtag needs a page like this. Otherwise the vast amounts of knowledge and culture created daily will be as ephemeral as the tweets themselves.