This is a marketing forum so we here should have a better idea about how the public likes to focus in on emotional and controversial stories, even if they are just anecdotal. We should also have a better idea about how the "news" is mainly about making money, not about covering what is most important.
You're right, 50 or whatever murders do happen every day in the US. People can't get emotionally involved with 350 victims and 350 suspects a week though. Focusing on OJ Simpson, Jon Benet Ramsey, or Casey Anthony for a month is better for tv ratings than covering 1,500 cases.
Brenda's story about losing weight is more powerful and inspirational to the general public than charts and graphs or interviews with scientists talking about thousands of people loosing weight.
Obama is about as "white" as Zimmerman. The racial angle is obviously there, but if Trayvon had been 40 years old and was friend's with Zimmerman, and the death happened after the two had got into a fight in a home, the media coverage wouldn't be what it is.
A "child" walking to the store to buy candy getting killed in the street by a gun -- there's plenty of emotional triggers there that have nothing to do with race. Marketers use emotional triggers to make money and so does the media.