A very reasonable-sounding idea is “Privacy is just a feature”. So you can focus on other things now (especially: getting more users!) and add privacy later. But privacy is not a feature you can add — it is the *absence* of uncontrolled data leakage. Two implications:
1. You can’t add it without breaking existing systems and user behavior.
2. You can’t succeed by partially adding it. Eliminating some but not all uncontrolled data leakage usually leaves *enough* uncontrolled data leakage to prevent most use cases.
2. You can’t succeed by partially adding it. Eliminating some but not all uncontrolled data leakage usually leaves *enough* uncontrolled data leakage to prevent most use cases.
(By the way, Zcash t-addresses don’t have this problem, because we thought this through. People who opt in to using Zcash z-addresses today immediately get good-enough privacy, i.e. sufficiently low uncontrolled leakage of their data.)
Note that the key word is *uncontrolled*! Most people are still confused about the difference between “I get to choose who sees what parts of me” vs “Nobody gets to see any part of me”. Privacy isn’t about isolation—it is about consent. (For both businesses and individuals.) ៚
P.S. Jack Gavigan (Electric Coin Co) chimed in with a great metaphor for summarizing the technical point here: “Better to build something watertight and add taps to let the info out than try to plug a sieve.”
