I was gonna say something about phone numbers and network analysis, but the link above said it better.

>>1 Mobile number

>>Unlike obsolete encryption systems, we require mobile phone to register in our system. Your account is tied to your phone number. Never mind that in many countries around the world SIM-cards can be bought only after presenting a legal ID, and that mobile networks themselves have all-encompassing LI (Lawful Interception) interfaces by design. Also let's ignore the fact that mobile networks still heavily rely on SS7 protocol stack from the 70s, with the security model based on gentlemen's agreement. Some people claim that words "mobile network" and "secure" can't be used in the same sentence, but our security experts think it's very safe. Do you guys not have phones?