We literally hand over our most private data, our DNA, but we're not just consenting for ourselves, we are consenting for our children, and our children's children. Maybe we don't live in a world where people are genetically discriminated against now, but who's to say in 100 years that we won't?
In every community, there are a number of 'social super-spreaders' among us. Long-suspected and emphatically confirmed by our data, these are people who - through dint of their job, or lifestyle, or perhaps even genetic makeup - would be more dangerous in the instance of a pandemic than the average person.
You can harvest any data that you want, on anybody. You can infer any data that you like, and you can use it to manipulate them in any way that you choose. And you can roll out an algorithm that genuinely makes massive differences to people's lives, both good and bad, without any checks and balances.
No weather forecaster can tell you for sure when to wear a rain slicker, stock up on canned goods, or evacuate a city that's in a cyclone's path. All forecasters can offer is their best guess at the atmosphere of the future, whispered by the simulated blue marble and wrapped up in uncertainty.