In the past month Kosovo has seen two violent deaths of Serbs in Kosovo's South. This comes after a long quiet period so the question is justified if this may be related to the tensions in the North. I think it is and I think this makes NATO responsible for those deaths.
The standard role of peace keepers - as NATO still wants to call itself - is to guard the peace while either the parties involved negotiate for a solution or some international authority like the ICJ or the Security Council takes a decision. This means that peace keepers should guard the status quo, only make changes when absolutely necessary and then do that preferable in agreement with the parties involved.
NATO is clearly overstepping its role as peace keeper and following a pro-Albanian policy. The message from this to the population - both sides - is that NATO is partial. That message is not restricted to Northern Kosovo but is visible to everyone. You can see it in Kosovo Albanian politicians who speak with more confidence. You can see it on internet forums where Albanians write with more confidence and you see it also in the increase in incidents that seem to reflect a growing Albanian assertiveness in Southern Kosovo.
The latest incident, involving usurped Serb-owned land, is in this respect illustrative. Usurped land has been a problem in Kosovo for decades and it has become specially acute after the 1999 war. A lot of effort has gone in handling them but the procedures stay vague and progress is slow. There are still many thousands similar property disputes that could get out of hand.
Peacekeeping is supposed to create stability, but NATO has created a climate where everything is fluid and Albanian efforts to grab more are rewarded rather than discouraged. One may not like the stability because it contains some injustices, but it is not the task of peacekeepers to judge what is unjust or to solve injustices. As the murders in Kosovo show there is a balance between injustices. Repairing those for one side while ignoring those for the other creates problems rather than solving them.
One could argue that NATO just wants to create a better equilibrium. But changing an equilibrium is always risky. Not only the loser has to consent. The winner has to consent too that there are still limits to his power. And until the new equilibrium has been accepted both parties may do anything to improve their position.
Every modern country consist of equilibriums. We have constitutions and laws that define them. For example the power distribution between the states and the federal government in the US is clearly defined. If the federal government would transgress its boundaries anything could happen. But where the US accepts internally such boundaries it behaves to the outside as if it is the absolute superpower who should determine everything. This is a very dangerous thing that does not only harm the relations of the US but also all the situations it wants to influence.