Actually I don't think this issue is clear legally. In NBA v. Motorola it was taken into account that Stats Inc gathered the statistics themselves which is not the case here. Plus at least in some jurisdictions there is the "hot news" doctrine that protects breaking news even though it is a fact. So the disclaimers are not empty nothingness, it is still a legal grey area.
e.g.
http://bits.blogs.nytimes.com/2008/06/16/the-ap-hot-news-and...
Right or wrong, for Twitter it's not even worth the risk or effort to test if that is true or not. Google/YouTube operates the same way: killing the account and taking the PR griping is cheaper than paying lawyers to sort it out.
IANAL, but I've been working on 1st Amendment stuff as a layperson since 1997.