This strikes me as less secure then a password manager that stores passwords. Here, if someone gets my master password all is lost. With stored passwords, they'd have to get both my master password and the encrypted passwords.
It also lacks what you might call 'forward secrecy'. If someone gets access to my master password and an old 1password backup, then they get all the passwords in the backup.
But with this, if someone gets access to my master password, they get access to recent passwords, and when I create new passwords they get access to those too. If I'm not aware that my master password has been compromised (why should I be?) then I'd be merrily creating new passwords that are compromised at the moment of their creation.
> Here, if someone gets my master password all is lost.
Not true. They'd need to know your keywords, which don't necessarily have to be "github" or "facebook" -- e.g., you could choose a consistent pattern, yielding "git##hub" and "face##book".
