A solid 8 posted a photo of a monkey on Facebook this morning. On a whim I decided to comment "Your long-lost twin?" for a goof. This could be taken as being rude, but she's a gorgeous girl and is probably used to getting her ass kissed (She ended up "liking" it anyway).
So my question is, how far do you take it when negging? Do you push it further and further and see what you can get away with? Does it depend on the hotness of the girl (I've heard that the hotter the girl, the worse you have to make the negs)? I've found that this neg might not work as well with a 5 or 6, because deep down they probably know they're not that hot and it's a look-based insult.