Of course, this 'effect' is only monitored via the single sensor of Google news. The site doesn't discuss "how" it knows where articles are discussing/linking.
As for other really useful interfaces to news, I'm a big fan of Newsmap, which displays news items as boxes sized depending on how "breaking" or widespread their coverage is. A good visual cue for determining what is seen as important amongst the news firms. But again, this is but a single source of data for a measure of "importance". It would be nice to be able to specify one's own gains for various criteria.
For example, say I am interested in news that occurs in western Europe, then America, then Asia, then Africa, and concerning the following subjects in descending importance: technology, science, arts, politics, sports. This set of criteria could be more expansive and then size events based on my interests.