Tether does not appear from thin air. It appears when new money is deposited on exchanges and OTC desks. It's simply a database for USD deposits. Some exchanges

Tether does not appear from thin air. It appears when new money is deposited on exchanges and OTC desks. It's simply a database for USD deposits. Some exchanges use MySQL to track their deposits. Tether allows transfering deposits between exchanges, in contrary to MySQL-dollars. There's way more MySQL-dollars being "printed" than Tethers. People pay attention to Tether because it's a transparent system. If Tether is not fully backed, it's a problem for those who own Tether. Tether is not a problem to Bitcoin.