FWIW, if you had watched more of the video you'd have seen that they already managed to have an impact in getting the US government to send over military advisors and some basic technology for the Ugandan military to assist them in tracking this guy down. Which is a lot more than your average "like this shit on Facebook because the world isn't all happy fluffy pink bunnies" shit.
And to say that guys like him are a dime a dozen is a bit naive as well. While child soldiers aren't at all uncommon, especially in Africa, generally speaking they're employed in some sort of civil conflict that eventually has an end when the power shifts in the region in question. In this case, there is no such endgame for the army, but instead it is a way of life and something that will exist in perpetuity until such time as the group is put down--not just Kony, but the group as a whole, because no doubt if Kony alone is taken down three more will step up in his place to fight over the role. If you missed that part too and/or are ignorant on the topic, Kony has expressly stated that he's not after anything other than maintaining his status quo--leading that army because it makes him feel warm and fuzzy inside and no amount of peace talks, cease fires, or other attempts to stop the violence outside of apprehending him will stop it. In other words, he falls outside the definition of what poli sci geeks might call a rational actor, and more into the role of the self-aggrandizing leader but with a particular quirk--he has no country, just an army.
As far as other notable instances of the same levels of this sort of thing happening (in other words, entire military groups being formed out of abducted children rather than their simply being recruited too young--kids have played roles in conflicts all over Africa, namely in Rwanda, CAF, Chad, and Sudan, and IIRC Mugabe in Zimbabwe has his own version of the Hitler Youth in his army as well though they aren't actively participating in any sort of protracted armed conflicts that I'm aware of), the RUF in Sierra Leone is the only one that comes immediately to mind, and Charles Taylor, the architect of that group was extradited into UN custody and last I heard is awaiting trial in The Hague.
