I'm asking this as a serious question (not as a troll), because one of my firmly-held principles is that I never argue with anarchists.
In a voluntaryist society, how do you prevent coercive power structures from arising? Anyone who owns a lot of land/factories/newspapers/guns is in a powerful position, and has a plethora of incentives to abuse that power. Please don't misunderstand me, I'm not a communist troll - when I say "abuse," I mean coerce other people who are in weaker positions to associate in ways they'd otherwise not. The most obvious way to do this is if I have a lot of guns and I simply force people to pay me tribute or die. I've always felt that the principles of voluntaryism don't have a good comprehensive answer to this sort of problem beyond simply saying "well, we don't think it's a problem." Prove me wrong?
One last thing: I can see already that people are going to say that I've described modern governments above (i.e., "pay use tribute or we'll use our pile of guns on you"). That may be, but I'm asking you to describe how this would be prevented in your hypothetical society, not arguing that we don't already have it in ours.