Frustration

The Global Language Monitor identifies frustration as a key word in news stories about Obama recently, as opposed to anger and rage. A search on the New York Times website identifies 22 articles from today alone that include the word frustration, and it's not just in political articles. So what's special about this word? What differentiates it from anger and rage, and how does it change the meaning of an article or the perception of a political trend to say that people are "frustrated" rather than enraged?

I think frustration carries the weight of time more than rage does. Frustration is the manifestation of a build-up of anger and rage over time, in my opinion. So it makes sense that while words used in association with Obama were previously "anger" and "rage", but now those are replaced with "frustration" as the intensity of the emotion dissipates but the quantity continues to build.
It is not simply the job of newspapers to cover immediate breaking news, but to track trends. The New York Times has "Times Topics" for just this purpose. This topic is all about health care, and a simple search shows that the word "frustration" comes up on the home page for the topic. "Frustration" seems to indicate a period of brewing unrest, perhaps between stages of "rage."
It may seem petty, but to journalists who are struggling to convey issues without infusing bias and without being excessively wordy, differentiating between rage and frustration can be crucial to the effectiveness of the article and readers' understanding. I think tracking the occurrence of the word "frustration" as opposed to the word "rage" would be an interesting task in newspaper reading. Seeing how words are used in context is important for the sake of getting the best understanding out of news stories, and being able to build upon prior knowledge and prior newspaper readings in order to get the fullest meaning out of every word of every story.