But who checks to make sure what is being altered is right.

Well, I guess everyone and no one. It's grasping the anarchy that is the internet and taking it to a new level by trying to make something for the public good. Being an encyclopedia they would want to incorportate all views on something, I think, but the veracity of certain facts is based on letting people who know provide the right answer. It all rides on courtesy really, so if it doesn't work, I guess it tells us something about ourselves. It's a study in sociology, somehow similar to this place.