On twitter, " 地震で死んで下さい " has been trending. Curious, decided to read the tweets, and it all points to a Korean youtube who rants in poor Japanese in a video once titled " Japanese people, please die in the earthquake ".
In the video, that he posted exactly on March 11th, he rants about Japan being nuked, the possibility of Tokyo being hit with another major earthquake making him happy, and more glee over the fact that the Japanese are apparently self destructing over themselves.
Hi, Japanese people. Good evening. Ah, have you've already been nuked (received radiation) yet? Wow, that must be really scary? Soon, Tokyo is also about to experience another major earthquake. Will you all die? That is just wonderful. When I think about killing people, I imagine them to be Japanese. Though, I think I don't have to kill any Japanese for real. They're already doing it to themselves. Ah, that feels good. While I watch over your reconstruction, I'll enjoy myself. Please, this very moment, die Japanese people.
After getting an onslaught of flames, the youtuber, xgyaruox, makes another video in poor English telling Japanese people to not " hate him " for his opinion/joke/whatever.
He also posts more videos that you can find here.
EDIT: after looking at this bro's channel, looks like he might not be 100% all there.
EDIT 2: He also has a video, more like description, explaining why he did what he did here. It's tl;dr.
EDIT 3: He's just pulled down his account. In his explanation he basically said that he did it because he noticed a lot of anti-Korean hate from Japanese on some site (assuming Youtube). He also mentioned that he used to like Japanese manga, anime, and music. But the apparent anti-Korean sentiments angered him. From what I remembered.
EDIT 4: Thanks to fuzzyspider you can view this poor bro's insanity again -> http://www.youtube.com/user/up5091
Source: twitter, that bro's youtube and various other online news sites