If I'm understanding correctly... This merkle tree should give clues as to how many users whatsapp has (unless they insert fake users - but either way, it gives a lower bound). It also allows me to see how often a user re-registers (ie. sets up a new phone).
Currently, I can see that if I have a conversation with a user, but with this public log, I can see the same info for the whole world?
Currently, I can see that if I have a conversation with a user, but with this public log, I can see the same info for the whole world?