I have been playing in a long running campaign in which party conflict, or at least the possibility of it, is very much encouraged by the DM. The party is divided, and we are very often thrown into scenarios that might provoke one side to attack the other. Interestingly enough, it is the "good" characters that are always the ones more likely to threaten an attack, and the "evil" characters that are always playing the peacemaker.
Most of the parties get along splendidly, or well enough at least. But killing of characters does happen from time to time. It has been a long time since it has been a knife in the back, but that has happened too . . . .
And through it all, we have remained the best of friends.