That's kind of a "man bites dog" headline, but it's what researchers at University College London found, according to this report in the Economist:
Sexual allure is often hinted as being the prize for buying this or that. Yet advertising wares during commercial breaks in programmes with an erotic theme can be tricky: the minds of viewers tend to be preoccupied with what they have just seen and the advertisement is ignored. New research now suggests that even if the commercial is made sexually enticing, people still fail to remember it.
Ellie Parker and Adrian Furnham of University College London devised an experiment to test three ideas. The first was to confirm that men and women alike would struggle to remember the brand of a product that was advertised during a break in a programme that contained sex. The second was that commercials that had an erotic element would be recalled more readily than those that did not. Finally they wanted to know whether people would remember the advertisement more easily if its theme contrasted with the programme into which it had been inserted.
The article describes the experiment, and its findings: sex doesn't seem to really make people remember ads, and therefore, we might assume, it doesn't sell much. Unless, I suppose, you're selling something like condoms. And they tend to be advertised with images like walking on a beach.