Jay Rosen debates the question of news context on Rhetorica. He writes:
There is no such thing as Context with a capital C. Which context to add is a debatable decision that cannot be governed by any existing rule set in journalism.
He goes on to say that journalists wishing to provide context to the Katrina story could cover everything from levee funding to questions of race and class in New Orleans.
But I think he makes too much of it. Here's a simple test for necessary context: Is the story misleading without it? For example, if you point out that Company B's stock has risen 5% in the last year, but neglect to mention that it's still 80% under its 2003 peak, the reader's getting a false picture. If you write that a Democrat on the judiciary committee is supporting one of President Bush's Supreme Court nominees, you should also mention that eight or nine others are opposed or uncommitted.
Simple stuff. The point is that news writers are usually covering only a sliver of history. They often can provide the necessary context with a thoughtful sentence or two--and too often they (we) forget to.