Fuck Everything, We're Doing Five Blades!
The Economist drops a little science on the diminishing returns of multi-blade cartridges:
It is simply not possible to add a new blade whenever the marketing department wants one. Every additional blade, explains Michele Szynal, a spokeswoman at Gillette, adds weight and size to a razor. Firms must therefore find ways of making both razor and blades lighter, which means thinner blades, more closely spaced, made of special materials, with new coatings.
—The Economist, http://economist.com/displaystory.cfm?story_id=5624861