Sequoia-backed RockYou, the second-largest widgetmaker on Facebook, is considering plans to staff a New York office with 2-5 ad salespeople — copying a move made by archrival Slide two months ago. Funny, it normally doesn't take these two so long to imitate each other. It's a much-needed move: RockYou has a reputation for being slow to respond even when advertisers come knocking on its door. The startup has been content to coast on charging other appmakers for promotion, and we hear it's on track to take in $10 million in revenues this year. But at some point, the company will have to give up that business model — which strikes some as suspiciously pyramidal — for legit dollars from Madison Avenue.