On CNN, longtime media critic Howard Kurtz writes how easily the media can be hijacked. About the GZ/TM case, he says:
Racial tension can grab the media's attention like few other issues.
There are more than 15,000 murders annually in the United States, but only a few move beyond local headlines. The killing of Trayvon Martin, initially overlooked even in Florida, became a national sensation once activists persuaded the media that race played a role in the teenager's shooting (a perception deepened by NBC's misleading editing of George Zimmerman's 911 call). Week after week of routine murders in cities such as Chicago barely register on the radar.
I agree, except the local media (i.e., the Orlando Sentinel) didn't overlook Trayvon's death. http://www.cnn.com/2013/01/03/opinion/kurtz-fiscal-cliff/index.html