[vitus]

They might be interested in all data if they had easy access to it and could filter it as it came in.

On the other hand, if they're tapping even a 100 Gbps link that's run at 50% average utilization, over the course of a year, that's more than 300 EiB of data. This is a frankly stupid amount of storage for such a tiny cross-section of our actual traffic. And I'm supposed to believe that they actually want to do that for years, storing zettabytes (or even yottabytes, depending on the scale of such a collection effort) of traffic in aggregate, on the off-chance that they have a quantum computer in 30 years? Tape storage might be cheap (on the order of single-digit dollars per TiB), but even at that price, just 1 ZiB is billions of dollars.

Sure, maybe you could reduce those numbers by performing targeted wiretaps, but it's also way easier to just subpoena Google and ask them to provide search history for individuals on certain dates...