When is a news story done, played out, way past its expiration date? What is the shelf life of an American media tale?

News events are radioactive entities with half-lives determined primarily by when the next item comes along to displace the last one.

The relative importance of the tale hardly matters.

A diaper-wearing astronaut confronting her romantic rival in an airport parking lot is pushed off talk shows by the lurid death of Anna Nicole Smith, a sad celebrity whose biggest headline was her last.

In the case of Don Imus, not even an apology, a pink slip and three innocent lacrosse players could stop it from moving forward.

Along the way, the 66-year-old morphed from a man with a trash-mouth reputation insulting scholar-athletes to a naif caught in a lame attempt at hip-hop humor to a First Amendment martyr, entitled not just to free speech but a multimillion-dollar broadcasting gig.

And just when the talking heads seemed about to blow up and the rest of us were ready to give up, someone shoots 32 people on a peaceful and beautiful Virginia campus before killing himself.

Then, just for a moment, this story of life and death at Virginia Tech straightens out priorities.

Blacksburg isn’t Baghdad. But in a few hours, lives can be taken just as quickly.

Young men and women, nurtured and reluctantly released into the safe haven of a college campus, and teachers there to help them in their journey to adulthood were killed, suddenly.

Time to reflect on the randomness of violence, to realize that nothing is certain. You’re promised nothing, not even the “nice day” a reflexive morning greeting wants you to have.

The logical next step is mourning.

What we’ll also get is the script. Yes, there is one, even for horror.

Because the violence is gun violence, statements of concern will mention the constitutional right to bear arms. The case will be made for and against gun control.

Media blanket the small town and we watch – because it’s important – and wince when a wounded kid with his arm in a sling tells another interviewer his story.

Experts will debate whether it’s the blood-obsessed culture that’s to blame or a young man with a list of grievances and two loaded weapons.

Shrines sprout, personal messages and handfuls of flowers to remember the dead for how they lived, not died. The heart of the families and witnesses surprise, as we wonder how we might act in such a terrible moment. Will we ever get that serious discussion on preventing the next senseless outburst?

The event that was Don Imus was supposed to generate a national discussion on race, gender and centuries’ old stereotypes given new life in gangsta rap. What we got were agitated hosts and their foils arguing on the same cable stations that turned the sagas of missing young blondes into an art form.

Let’s hope the events of the last week render those exercises meaningless.

Who’s the father of Anna Nicole’s baby?

Who cares.