As reported before on Slashdot, the Whitehouse is a Drupal user since October 2009.
There's a sizeable segment of the population which simply can't search properly. Being able to synthesize a question into appropriate keywords is a difficult skill for many. Try watching a novice search Google on a variety of topics. Not only will they use poorly worded queries, but it's likely they will only go to the first hit. Many users give up if the first hit isn't what they want. Only the advanced users know about tabbed browsing and will load up a series of results to scan.
So, the reason why users don't google it in the first place is that they don't trust search (though Google has some of the highest trust levels of any search engine). What really needs to happen is that workplaces which have users online need to offer more comprehensive training on internet literacy; unfortunately, it's cheaper just to hire someone to handle all of the stupid questions instead.
Actually, you can subscribe to just about any stream of data from twitter with RSS. Of course, most non-techies won't know how to do that, but it's quite possible to be a pure twitter follower with nothing other than an RSS client.
Where twitter accounts do become useful is how they're a bridge between the informal aspects of IRC and IM and the persistence of email. Rather then spamming your friends with email or IM with a link to an interesting news story, you can just tweet it, and give them the control to follow up, ignore, or filter as they see fit.
Logic doesn't apply to the real world. -- Marvin Minsky