But that's assuming that you're hiring more programmers to do the same task. Programming is partitionable at a larger scale - if I hire more programmers I can start more projects/create more products.
So I guess what I'm saying is that for a one product company, yes, there is a point where the productivity loss from adding another employee gets very big. But for multi-product companies (think Google, Adobe, Microsoft, Apple), more employees just means more parallel projects.
It would seem that way, but I seriously doubt all of those parallel projects exist in vacuum. They likely will share frameworks, they should certainly share UI elements and designs.
I mean, Apple can't have the iPad, iPod, and iPhone teams not talk to each other, their clearly linked on numerous levels.
Likewise, Microsoft's apparent reliance on "parallel projects" is why we geeks poke fun at them so much. Anyone remember the screen shot of the 20+ styles of Window decorations just in Microsoft products on XP? Or howabout the fact that the Windows team has to basically reverse engineer (or at least re-develop from scratch) all of the UI features of the Office team.
So I guess what I'm saying is that for a one product company, yes, there is a point where the productivity loss from adding another employee gets very big. But for multi-product companies (think Google, Adobe, Microsoft, Apple), more employees just means more parallel projects.