[chipotle_coyote]

> You can choose a username, instead of a phone number

Unless this has changed recently -- and I can't find any indication that it has -- this is not true. You can choose a username in addition to a phone number, but you must have a phone number. Your username is effectively an alias for your number; your account is tied to the number, not the username.

[wyuenho]

Good point. I think a better description is both the phone number and the username are tied to the account, and you can change both at will. There are enough privacy settings in Telegram that can effectively turn off having your phone number show up anywhere. You disable contact syncing and even delete synced contacts.