It's not just that ppl have the data and use it for amoral/unfair purposes. It's that people come to trust the data, believe in it and use it to make decisions. This is disastrous b/c there are huge margins of error.
Errors are possible at all levels in systems like this, including sabotage and incrimination and your suggestion of junk data.
E.g. in the motorcycle example cited above. It's quite possible a motorcyclist needed to stretch their legs, so they pulled into a driveway for a moment, stretched, then google snapped a photo, then it was used as evidence. It's not likely or common, but it's utterly possible and not anticipated by these systems.