Technically, Twitter says you keep the right to your words.
If you wanted to give up the rights to your words, you could use something like tweetCC (http://tweetcc.com/) to apply a Creative Commons license to your tweets.
Actually, Twitter just says that they don't claim any right to your words. ("We claim no intellectual property rights over the material you provide to the Twitter service.")
Whether you can copyright text as short as 140 characters is at least debatable-- it may be that nobody holds copyright over tweets.
Doesn't matter what Twitter says if the utterance itself isn't copyrightable by anyone.
Jobenjo has a point about haiku -- but questions will seldom be recognized as poetry.
Indeed, as a question gets better as a question, more concise and precise, it becomes more like a pure idea, or a strictly functional communicative construct. You can't assert a copyright on those.
I'm pretty sure that Fluther's TOS doesn't apply here since Mahalo never used the site.