A matter of impact.

In the wake of Steve Irwin's tragic (and as WWTDD? noted, cruelly ironic) passing, many fans have been understandably in mourning - but we've also had the inevitable harder thoughts. One, of course, was from professional shit-for-brains Germaine Greer so we won't pursue that any further (but you can read ithere and go to others from there) , and there are also the inevitable sick jokes (including an adjusting of the Wikipedia entry on Stingray to include a reference to the Hunter- now cleaned up), but another was on a blog that brought forward the inevitable "Why are the media going overboard over this death and not such and such?" response.
While it's understandable that some feel that way, there's actually a reason. Yes, it's appalling when masses of people die en masse. And yes, it's horrifying when people are murdered in savage circumstances. And no, they shouldn't have their tragedies neutered or watered down in any way. But... but how widely known was Stephen Lawrence before his racially-charged murder? Or JonBenet Ramsay? Or that girl who escaped after being held captive in Austria for years? And how individually known are the casualties of war? Or the 9/11, Bali, Madrid or London bombings? We can't put faces to all the victims, and that's probably a good thing - if we kept getting it in our faces at high levels of impact all the time sooner or later we'll all get desensitized to horrifying and undeserving fates. And I don't want to be desensitized; I want to be in horror at death, both fictional and real.
Being famous put Irwin more at a one-on-one level with people; they didn't know him, but in a sense they sort of knew him as a familiar face - as a character - as a hero. As a sort of friend. When you can put a face to someone and you admire that someone, hearing about his passing makes it hurt more than if it was as part of a natural disaster or war strike, and that's why there's so much news focusing on the end of the Crocodile Hunter. Domestic outrages are outrages, but they don't resonate much worldwide (again, not to imply they're not important, because they are); Steve did.