A yes/yes-er is someone on MySpace who selects the option Yes/Yes for Smoke/Drink under "Background & Lifestyle" when they update their profile. A variation on this could be a no/no-er, a no/yes-er, and the quite rare yes/no-er.
Girl #1: Oh my God, he is so cute.
Girl #2: True, but look at his MySpace... he's a yes/yes-er.
Girl #1: ...gross.
Boy #1: Check out that girl over there. I had no idea she went to our school.
Boy #2: Didn't you hear? She got expelled from her old school because they found her MySpace profile and saw all her partying pictures.
Boy #1: What's so bad about partying pictures?
Boy #2: When her principal asked if she was a yes/yes-er, she lied. Then they found her MySpace. With all the pictures.