A user can only signup to our system via an invitation from existing ploiny users.
If a user trust's a friend, he can invite that user by sending an invitation to his email address.
To invite a friend, the friends' information must exist in the ploiny system, the user selects who the friend is and is taking responsibilty that this information is accurate. If at the end the friend turns out not to be the person stated, the user's accound will be terminated.
The invited friend then creates an account and picks a username