I don’t disagree with anything you said here, but it reminds me an argument about IRC privacy from the ’90s. People frequently accused IRC networks of secretly logging private conversations, and the usual argument was that this would require such an immense amount of storage that any such effort would be astronomically expensive and entirely infeasible.

I don’t know if that was really true even back then, but today it’s completely doable and done all the time (think Google Chat or Facebook Chat).

My point is, times change, it’s entirely possible that in 20 years storing that much data will be completely possible.