Because there is no first factor. You don't log into Dropbox or Google with *onl...

		jrockway on Aug 27, 2012 \| parent \| context \| favorite \| on: Dropbox Introduces 2-Factor Authentication Because there is no first factor. You don't log into Dropbox or Google with only your OTP, you use a password and OTP. With the method above, you scan a code with your phone instead of using a password or OTP.