I find that as companies get bigger, problems get larger in number. I've always attributed this to a lack of understanding and communication between the various people. One person designs a part and specs the way it will communicate to the outside devices. Another designs a different part and follows this spec. Unfortunately, due to unforeseeable differences, very rare cases will put the system into a failure mode. When analyzed, the problem is obvious. The issue is that one person did not overlook the entire design (essentially do the whole thing themselves).
Two seems like the magic number. There is only one other genius to ask to make sure your genius did not take a hike into a black hole. However, most of the greatest things so far have been by one person solely. Talks of dualities in these people is common
Ying and Yang. Relativity. There's no good without bad, there's no 1 without the 0.