So Saudi Arabia has invested $3.5bn in Uber, the ride-hailing app, making it the largest single investment ever made in a private company. Talk of war chests and global expansion abounds. But perhaps what the above really implies is that Uber’s famous capital-light model is about to get much more capital intensive — especially as it moves towards rolling out the much hyped self-driving fleet. If that’s the case, investors need to pay attention. Along with capital intensity come limitations to the exponential growth rates investors have come to expect.