@rune @sir As I already said, any not federative (to be honest, not f2f system) can not guarantee that it will not collect you metadata. Sad but true. Phone number reveal is not a big deal in that circumstances, as you still leave other fingerprints. You can reduce them, but not completely.
More over, in countries outside the NATO or do-not-remember-how-much-eyes, the threat of metadata leaks drops significantly, as it will be not easy to get to this data.
@peexea as soon as you have to argue with "only these few can get your metadata" it's over though. rubberhose some admin
at openwhisper (or his children). even the mob can do that. with how insecure the phone networks are, having the number is a pretty big deal.
anonymity and privacy aren't easy problems to solve, if they can be solved at all. telling people otherwise is dangerous and requiring their phone number for "convenience" borders on evil.