To get around Bayesian filters, some spammers have resorted to ASCII art, spelling out words with characters and really small text.
I've been online long enough to remember when people used to create ASCII babes you had to print to view. Back in the late '80s, whenever I retrieved a printout from the University of North Texas computer science lab, there were always a bunch of suggestive or even explicit ASCII trollops waiting to be picked up.
It wasn't easy for the object of your affection to be vulnerable to smudging.
Who needed to worry about smudging, considering you couldn't even -see- the picture unless you were 20 ft. away?
Occasionally at RPI, a bulletin board at the end of a long dorm hallway would be decorated with a 6ft. ASCII Playboy centerfold. Talk about desperation :)