However, users should be incentivized to write short bits, but it should be easy to go longer without cluttering up the timeline, and forcing the author to use a different piece of software. The writer should be aware they've gone over a boundary, but should not get an ease-of-use penalty for it.
The idea of having Twitter (or app.net or whatever) be something separate from a blogging system is causing inefficiency and miscommunictation.
Some people know how to write efficiently and don't need a crutch like a character limit to keep it concise.
For example, a lot of my emails are less than 140 characters, even though I have unlimited space.
Another example, this blog post explains why you would want a Twitter system capable of more than 140-characters. Yet over on Twitter, so far, all the responses have been basically 140-character limit is good. My guess is that most of them didn't click the link or read the post. And I don't think the idea in this post could be explained in 140 characters. Not in any kind of convincing way.
There are ways to do this that work better than the current method (using a different website, writing a blog post, etc), but all of them require changing the user interface of the Twitter app. Since Twitter is not extensible this way, and since it's illegal to create new Twitter clients, to solve this problem will require creating a Twitter competitor.
For a hackathon, this isn't a problem, where the goal is to expose an idea, not make a product. And if the idea is compelling enough, it might spawn a new market. We certainly need to get out from behind the limited thinking at Twitter, Inc. Imho of course.