CBS Outdoor and Clear Channel rejected some billboard ads from San Francisco's St. James Infirmary, a clinic run by and for sex workers and their families. The work shows men and women of various ages and ethnicities along with the tagline, "Someone you know is a sex worker."  Those last two words tripped up CBS, which told the clinic in an email that "sex worker" is "not a family-friendly term," but that it might reconsider the ads if different language were used. What did they have in mind? I doubt "prostitute," "porn performer," or "phone-sex pro" would've passed muster either. The ads will now run, unchanged, on 50 Muni buses  in the San Francisco area. They seem pretty tame. The really shocking stuff takes place in the seats way in the back. More posters after the jump.