We’ve know for over 35 years that “adding manpower to a late software project makes it later”. Amazon has it’s two-pizza team heuristic: “If a project team can eat more than two pizzas, it’s too large”. The excellent Code Complete has a detailed explanation of how communication costs increase with team size. Yet we still need reminding.
Dhanji R. Prasanna has an excellent retrospective on his time on the Google Wave team. He sums up the problem with big teams very well:
And this is the essential broader point–as a programmer you must have a series of wins, every single day. It is the Deus Ex Machina of hacker success. It is what makes you eager for the next feature, and the next after that. And a large team is poison to small wins. The nature of large teams is such that even when you do have wins, they come after long, tiresome and disproportionately many hurdles. And this takes all the wind out of them.
For me, that’s really the crux of it. As a programmer, it kills you to not get stuff done. Large teams necessarily involve more communication, more complexity, and less getting stuff done. Large teams are a programmers equivalent of retirement.