Keep in mind, though, that even "friction" will eventually cause a team's productivity to drop down to 0. The amount of friction that a given team can tolerate depends on the team members, of course, but especially on the size of the team (see: Mythical Man Month).

There comes a point that even a tiny bit of friction, spread out over enough developers, eventually causes the marginal productivity boost of adding new devs to reach 0. That can happen even without friction, but the friction exacerbates the trend.