[kichik]

And it can't accommodate websites having weird password requirements. Some websites require symbols and some have maximum number of characters. Fixing this would probably require special characters in the keyword which would force you to remember the website's original password requirements on top of the keyword itself.

[yoha]

Very good point! Since some websites still require PIN codes (passwords made of digits), you would have to restrict yourself to something like 8 digit long password, which is not very secure, even with a slow hash (scrypt iteration).