Mark Twain quipped that "Faith is believing what you know ain't so." Love can be like that too -- a pathological condition that makes one "unsee" the failings of the belovèd, often to one's undoing and everlasting regret.
I asked my friends many times and their answers were ‘i don't know’ so according to the arabic proverb love is indeed blindness as many who say that they are in love usually come some time later and say they have a problem :)