Google has just indicated that double authentication will soon be activated by default for everyone. It now represents the easiest way to avoid having your account hacked, even when your password has been leaked. Google wants to highlight this essential security feature, which is too seldom used.
A simple password is no longer enough to guarantee secure access to an online account. One of the best ways to protect your account (Google or other) is to set up a second form of verification, in order to prove that you are the rightful owner.