Do you recognize your friends’ friends? I do. My friends often talk about their friends to me. Sometimes I pass them on the street. At first, I put a smile, but most of them don’t recognize me. In this modern world suspicion is a must, so you can’t smile freely to another person. Yes, even in Indonesia where people are labeled as friendly.
After several smiles, I learn to stop. I don’t greet the persons anymore. People don’t like to be ignored, right? It’s embarrassing and also tiring (mentally). Ironically, some people start recognizing me after I called it to quit. It seems they’re having slow adaptation to the greeting. That’s weird, I read that in the adult world we greet a stranger and he/she would reply as a token of manner. I think the suspicion defeats manner. 
So, I think it’s best to introduce your friends to your other friends, even though we’re having a different circle. At least, you can judge me better. And I will know you will not be lonely if I’m not around. Haha. Who knows they might clicks and become friends. And ultimately, it saves me from embarrassing myself by waving to confused people.