> Each SDK might be tattling on you, but unless you give them a key to match you across apps, each signal from each app is unique

You'd be surprised what can be done when data from different source is fused together.

Large-Scale Online Deanonymization with LLMs: https://news.ycombinator.com/item?id=47139716

Robust De-anonymization of Large Sparse Datasets: https://www.cs.cornell.edu/~shmat/shmat_oak08netflix.pdf