let the guy code sheesh 

ive been reading a fair amount  about brain wallets. they fascinate me

ive heard some pros and some cons. the main reason against them seems to be that

1- people use very common phrases (lyrics to songs etc)
2- people have poor memory

but if one were to use an uncommon phrase (say a foreign language idomatic expression) and they securely stored the phrase, would the brain wallet fail

additionally ive seen some brain wallets add an extra password to help the seed

given the above assumptions, at a technical level, is there reason to believe brain wallets are not to be used other than what popular opinions feel?