I don't know if the knockout game is really on the rise or whether the issue is even important, but I would caution against the general pattern of seeing a blog post which seems to confirm your assumptions and then crowing triumphantly without really engaging the issue.

The blog post you're relying on to describe this as a bogus trend is extremely weak. It offers no new research or evidence and uses faulty logic in at least some parts. I won't write a full takedown but this part seems like a pretty glaring logical error. The blogger points out that an anonymous "Dutchtown woman" says her white son participated in a knockout game and that it isn't a "black thing." The blogger then asks:

How could Torres read this article and yet still come to the conclusion that the assaults are on the rise and that “most” of them involve black assailants and white or asian victims?

Probably because Torres didn't just rely on the opinion of "one Dutchtown woman," looked at the other available articles where racial descriptions were available, and made conclusions based on that.

I was watching a "Caught on Camera" show this weekend about the worst courtroom incidents -- shootouts, stabbings, etc. Really horrible stuff. And I thought, "Wow, the world is pretty bad and crazy and humans can be really awful."

Then, on my way to work, I was driving through the suburbs, listening to some goofy morning show and thinking, "Hm. The world is pretty good and mundane and human beings are mostly really cool. That show made me believe something worse than reality."

The truth, of course, exists, where the world is exactly x% good and human beings behave at exactly x% coolness, regardless of how I feel about it after being exposed to some crazy badness on TV, or some normalcy during my commute.

In your examples, you seem to have something simlar: Sensational account of violence vs. a blog saying that the media picks stories they think are sensational.

I think it is probably a good heuristic to think to yourself "Calm down. They get paid to show interesting and scary stuff even if, and maybe expressly because, it is super rare" while watching the news. But I don't see any data here to conclude anything about the "knockout game".

Sure, this bias exists in journalism (including blogging). A report that confirms existing social biases will sell well and be widely reprinted or linked. It gets people talking about the topic. People double-count evidence when they see multiple discussions of the same topic without realizing that those discussions are not at all independent. Further reports will re-analyze borderline cases as belonging to the "troubling new trend". And to most audiences, fear sells better than debunking.

The bit about one writer digging for examples of "black mob violence" seems to be something different, though. It's portrayed more as a deliberate one-sided evidence search than as double-counting. Perhaps worse, there's the self-defending theory angle: "I know this trend exists, so when someone disagrees with me that a particular incident is evidence for this trend, that demonstrates that they are trying to cover up the trend."

What really bugs me, though, is that debunkings can play into the availability heuristic. I'd never heard of the "knockout game" story before reading this post. And people are better at remembering stories than at remembering which stories are fact and which are fiction.

and it's especially significant that the article is from two years ago; this is not the first time the media has tried to get people scared about this "trend."

Conversely, it could mean that the media did indeed notice a trend two years ago and now the trend is picking up.