If you're in someone's in group, they'll always be willing to help you. You can tease each other, and it's no big deal. You can borrow money without losing face. If you're not in someone's in group, if you're on the outs, fuck you very much, it seems. Sometimes I purposely ask people who aren't in my in group out to lunch. It's interesting: either we have a meal together and get closer, or I learn to recognize lies.
1: "Do you want to have lunch this weekend?"
1: "You know all the good places. I was hoping you'd tell me."
2: "OK. I'll call you and let you know where."