a billboard in Times Square:
As far as I knew, Gossip Girl was generally targeted toward tweens and teens--the same kind of people who were addicted to The OC all throughout my time in high school. This ad would suggest otherwise, irrespective of the fact that it was two stories tall, and located right off 42nd St (one of the busiest streets in the world, including a very large number of tourists and young children). It doesn't just denote sex, it connotes it as well. Without my knowing the brand, it could seem as though it came right out of a porno or graphic photo shoot, and had just been cropped to remove any nudity.
Attention grabbing to say the least, especially when the not-so-subtle implications are that the show will contain much material along these lines. Taking it to another level, it could be argued that the powers that be at the CW want you to believe that watching their show will lead to you having more sex.
Finally, the tagline is simple, yet incredibly effective. "OMFG," which I don't need to spell out, could be referring to the public's response to the ad, or more likely, suggesting the kind of orgasmic exclamation the characters pictured would be emitting.
Only the text at the bottom clarifies the ad--it's actually somewhat shocking to realize that this is the face of a network television show. From what I hear, it's incredibly successful, so it seems that sex really does sell.