In the long run federated protocols and servers demonstrated their resilience regarding third parties and time, see irc for example.
Probably Signal is just a reference implementation, the big deal is implementing Signal protocol in different systems (whatsapp, allo, fb messenger..).
Having said that, I would be happier to not give my phone number for registration, and contact discovery but this is today a user interface well understood and accepted outside geek communities that's hard to eradicate.
In the long run federated protocols and servers demonstrated their resilience regarding third parties and time, see irc for example.
Probably Signal is just a reference implementation, the big deal is implementing Signal protocol in different systems (whatsapp, allo, fb messenger..).
Having said that, I would be happier to not give my phone number for registration, and contact discovery but this is today a user interface well understood and accepted outside geek communities that's hard to eradicate.