k-anonymity means there must be at least k persons (or similar) that have identical data in the dataset. E.g. with k=5 there has to be at least 5 rows for each

k-anonymity means there must be at least k persons (or similar) that have identical data in the dataset. E.g. with k=5 there has to be at least 5 rows for each unique set of column values. It's easily broken if multiple such datasets are combined. And that's probably exactly what the commercial surveillance industry does.