This changes the situation from "What was that password again?" to "What algorithm did I use for this site?", and given that I'm already pissed off at having fo

This changes the situation from "What was that password again?" to "What algorithm did I use for this site?", and given that I'm already pissed off at having forgotten my password, the likelihood of my remembering this goes down significantly. Which makes me even more pissed-off. IOW: When designing a scheme like this, the fact that you'll be angry when trying to actually use it at some point in the future becomes an important design constraint.