I am not convinced that it is a bogus trend. The frequency of reports has increased. I've been watching this trend since I first heard of it - also in 2011 - and this phenomenon - as well as the larger set of of unprovoked non-robbery related attacks by blacks on non-blacks - is increasing.
(Note that Hispanics and Souteast Asians also join the fun in one or more of the attacks on Jewish folks in NYC.)
Part of the problem is that most media will not report black-on-white crime as such, refrerring to offenders as "youths" and "teens". See here for many more examples.
If you want to see an example of the racial bias in news coverage, compare the coverage given this story to the Zimmerman affair and note the races involved.
ETA: More details on media coverage of violence:
The Knockout Game: Racial Violence and the Conspicuous Silence of the Media
ETA2: Thomas Sowell, himself African-American, commenting on this:
When I started seeing stories about the "knockout game" (supposedly, teenagers playing a game where they try to knockout random strangers) a few days ago, I immediately resolved to avoid paying attention to them, because it sounded like a classic case of people taking a few isolated incidents and blowing them up into a big scary trend.
And then this morning, I see this blog post, which links back to an article from two years ago titled: "Knockout King: Kids call it a game. Academics call it a bogus trend. Cops call it murder." Turns out my knowledge of human biases has served me well... 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." From the article (emphasis added):