But now we have a discovery problem. How do I find my current contacts? Do I need you rebuild my social graph from scratch? Good luck getting my friends with PhDs in computer science doing this, let alone my grandma.
Entropy is a double edged sword. IMO signal is doing a good job here. We can go drop phone numbers completely when enough people are using signal. But while the userbase is low it's probably worth the 3 spam messages I get a year. I get more than that in a week on my iPhone and more than that a month when I used Android. So I'll take the trade.
And I must stress, the phone number issue is about privacy, not security. At least with regards to signal