Securely storing information about a driver's trip on that driver's phone is hardly "offloading their costs to society." I assume the driver does not want the information about the trip they are providing to be lost, and therefore that they do not get paid, if an Uber data center goes down. This is not about storing all of Uber's data on the driver's phones (this would make no sense), only the information for that particular driver's activity.
Further, as the article describes, this may actually be more reliable than separate backup data centers.
This is the reason I don't use uber unless I have literally no other alternative. They continue to show a willingness, damn near an eagerness to make their drivers suffer for their unwillingness to work with local government by chipping away at the earning potential of drivers.
And even when I was out of work for a while-I've got a car that would be perfect for Uber Select, I refused to drive for them because their business practice makes it abundantly clear they do not care about you as a driver. You're a means to an end, no matter the cost.
I'm looking forward to the day when this "fat client" strategy will have lead to a "decentralized Uber" (based on open-source technology, etc.).