Occasionally I take the trouble to poke around for legitimate messages amongst those in my Google Spam folder then mark these "Not SPAM". They are not all that hard to spot. I guess that the more of us that do this, the less likely that these messages are treated as SPAM. All good and for a greater collaborative cause too.
It reminds me of a student that once figured out a snappy way to remove all the fascist red wiggle-lines that appeared under particular words in his assignments. During his creative periods of IT immersion and composition, these red flags would attract the attention of passing English teachers who would then challenge his spelling. He explained that all you had to do was right click then "Add to dictionary" then 'whamo', no more spelling mistakes and a return to the quiet of blissful isolation. He remarked that it didn't really matter, the teacher seemed to enjoy correcting the mistakes later.
I quietly groan when I consider this ignorance and the future of his growing dictionary of misspelled words.