You all seem to have forgotten the Bosnian war, which preceded the Kosovo intervention, and probably made it inevitable. After the secession of Slovenia, which was peaceful, racist Serbian nationalists were determined to punish further attempts to break away. This resulted in a nasty war with Croatian nationalists, which the Serbs lost, and the Bosnians, which the Serbs were winning- with well publicised atrocities- until Europe and the US intervened. This was probably the right thing to do; you can't let genocide succeed.
But the tactical decision to concentrate on bombing was probably a mistake, though understandable since it's not at all certain that the public would have accepted the casualties inevitable in a physical occupation. Remember that Yugoslavia had organised its entire defence strategy around guerilla warfare, and that every male was trained in the techniques; this explains much of the sheer nastiness of the civil war. But the bombing, particularly of the Danube bridges and the TV station, was an own goal in terms of winning over the non- extremist Serbs, who were forced into the racist camp.
Since its defeat in Bosnia, Serbia has been sulking like a wounded pit-bull terrier. The Kosovar rebellion was partly thickheaded nationalist, buit also partly deliberately provoked by Serbs who wanted to take out their frustration on the one minority they had left.
The situation is further complicated by the mis- selling by the neocons of a broken model of capitalism to the Russians after the fall of the Soviet Union. The result of mass impoverishment and the rise of a mafiocracy based on looted State property fed boneheaded nationalism there too- added to by the humiliation of seeing former client states like Poland, Latvia, and Estonia treated more favourably by the Americans and Europeans, even when (as in Estonia) they implemented discriminatory policies against ethnic Russians. So the Serbian situatuion is an ideal opportunity for them to infect the nationalist sores in central Europe.
America, and much more so Europe, have failed badly in failure to be consistent, to reward social behaviour and punish antisocial behaviour, and to prove that their commitment to democracy and human rights is real. It's not at all clear where to go from here, and starting from somewhere else would have been the better option.