I don't watch the news...
So I don't know exactly how much media attention this film got. Notice how many of the earliest reviews were very high; I wouldn't be surprised if the media blew that out of proportion to say that NG and the Internet in general foster sick minds who enjoy violence. A lot of the latest reviews are very low (many 0s and 1s). I can't tell if this is because people are biased because of the Jeff's actions and therefore score low or if people are too lazy and just give all 0s so they can give their opinion. Probably both. I kind of wish people would give fair reviews to this, as the flash itself (ignoring the violent themes and the fact that the author did kill people) is actually pretty good, especially for a first submission.
As for the "blame game" and how we have to monitor the Internet to find "telltale signs" of impending violence, I think that that's impractical since you can't tell who's a killer just by their actions on the Internet. People can be totally different people on the Internet and not like their normal selves. This isn't to say that these "signs" are meaningless; it's just that this flash alone isn't grounds enough to say/predict that Jeff Weise was a killer.