Apart from the sociological elements identified by Jill in the post, I still have to place this in the category of “local news become national to the extent that national and international news gets shunted aside” that I deplore in missing white girl cases, and, to a lesser extent, serial killers who are operating exclusively in one area.
I think the nationalization of stories which should basically be local ones is one of the not-talked-about-enough pernicious impacts of 24 hour cable news (and to some extent the internets as well). People are raped and killed every day, but some stories bubble up to the national media for bizarre reasons. In some sense this isn't really fair to the accused or the accuser, as the media attention they get is disproprtionate to the importance of the situation. It also gives viewers a rather distorted view of crime and the justice system generally in this country. And, it provides additional privileges to people who can afford celebrity lawyers/PR people who can spin their way into the press. They also of course take time away from coverage of stories of actual national importance. There are also the obvious race/class issues of which stories get national coverage and which don't, but even without that...