Beyond that, it's a power asymmetry as well.
If you have to collect info on someone "the old fashioned way" (like being siblings with them or marrying them) the power differential in the relationship is bounded by definition. To me, privacy is almost like a vector with two components—the level of privacy, plus the degree of intimacy of the relationship.
The amount of data Google has and the amount of data a government will have gives an order of magnitude advantage to whoever gets to harness it.