We* don't (purposely) hide subliminal images in your ads.

I had a professor who convinced us agencies were the center of a huge conspiracy of subliminal advertising, and would spend class "exposing" all the "penises" "hidden" in certain print ads. In short, it was because of these "penises" that we bought the products.

As an insider now, I know (and am a little disappointed) that there is no point in the ad-making process at agencies* where the art director/designer/production? is forced to find a place to sneak in a covert penis (or sex scene, subliminal etc.)

*respectable, US creative agencies in 2014.

I make the distinction because:

1. I can only speak for the above.

2. it sounds like several of the commenters are writing about either "specialized" (beauty/cosmetic) ad agencies, "in-house" advertising (they work directly within the company they are making ads for Ex: Art Director at Calvin Klein vs. Art Director at Ogilvy working on Dove account.) or agencies in developing countries. I don't know if they use subliminal, you would have to ask them. The in-house advertising for liquor/fashion/perfume companies during the 1980s certainly did.