As easy as it can be to get very anxious about things like this, I suppose it bears noting that “big data”, such as you describe, also provides baseline information, against which conspicuous patterns can be validly compared, and identified. No one is interested in, nor has the resources to examine, the banal and commonplace, but they need to know what the banal and commonplace looks like, on average, in order to recognize what is truly exceptional.
In a sense, it is analogous to highway safety checks. I would imagine that every officer out on the highway, stopping every vehicle to verify the driver isn’t impaired and that all applicable seatbelts are in use, assumes that 99% of the vehicles they poke their heads into are just fine and not really worthy of inspecting. But that doesn’t stop us in the driver’s seat from feeling “What are they stopping ME for? What did I do wrong?”.
Being a grain of sand in “big data” doesn’t necessarily stop those sand grains from feeling like they are under the microscope. Naturally, I recognize the difference between being a sand grain in the big data of Wal-Mart, Google, or your credit-card company, and being part of the big data of an organism that has much greater legal power to interfere with your life. Realistically, the risk is itsy-bitsy teeny-weeny small, but I understand why people feel like it isn’t.