Well, one way to think about it is to consider what the effect of the growth might be. What good is a corporation doing getting that large? Who benefits from the amassing of so much wealth? Are they acting for the benefit of many people, or are they more like a black hole -- mindlessly absorbing money and growing over time?

Certainly if a corporation can grow to get so large, it's hard to argue against it. It becomes a bit like a force of nature in that sense. But there are possibly repercussions to that, just as there would be repercussions if a black hole were to suddenly appear in our solar system.