I think we can answer that question fairly quickly - no. People got along with 2 blades for years and had no problem at all. (People shaved with straight razors and most still did okay, unless they had Sweeney Todd for their barber.) But enough people have embraced the three-bladed razor to make us wonder whether it really is an improvement over its ancestors, and whether that means more will always be better.
A couple of years ago when Gillette released its first five-blade razor, it seemed incredibly absurd. The idea is that the five blade system pulls hair out and away from the skin while it cuts it, which apparently gives a closer, more comfortable shave. The current model includes another blade for trimming, so although you aren't shaving with all six at once, it still has six blades.
Dermatologists say that any more than two blades will actually cause more razor burn and more pain. More blades means more friction - more ways to irritate the skin and more blades to nick it. However, are saying that they've solved those problems by putting the blades closer together, making them our of friction-reducing materials, and adding large guards to protect the skin.
The paradox is that most of the people with the most sensitive skin will actually have better luck with two or three blades. People with thicker hair usually do find that the increased number of blades can help their shave to last longer - a definite plus. However, those who have easily irritated skin will probably want to be careful before rushing out to by the latest in razor inflation - for the most sensitive, less is probably more.