In a way, this seems like an at-speed version of the Social Security Number's slow-motion train wreck: just as SSNs are not secret (and in many cases are actually pretty easily guessable), so too possession of a phone number is too-easily changed.

We need a good solution to identity. Right now most web services use 'has control of an email account,' while some others — to include email services — use 'has control of a phone number.'

I don't trust governments in general, so 'is vouched for by a state' doesn't really work either, although for many institutions (e.g. banks) that's probably good enough (if a government wishes to confiscate one's funds, it will do that, rather than create a fake driver's license and hand it to someone to clean one's accounts out).

Perhaps some sort of social identity is possible? 'Charles is vouched for by Alice, Bob, Dave and Frank' might work, although there's the issue that someone has to vouch for each of Alice, Bob, Dave and Frank — there's a Sybil attack where someone, or a group of real people operating together, could create false identities.

For my own accounts though, if I nominate two persons I work with, four persons I go to church with, four more in my family and three friends then I'd feel pretty good if nine of those were allowed to vouch for my email. I think.