Yes, this has always been an issue on the street. I adapted a shooting style for humans in the street that includes not putting camera to my eye until I'm ready to snap. That means everything is set before and I'm waiting for the right moment...however, standing still on the street corner is also problematic...so I tend to watch the street around me while walking around, spot a scene, set camera, and proceed to walk through the scene pausing briefly to compose, snap, smile like a fool, and keep walking...I think Winogrand did something similar... I avoid that which looks dangerous (young punks with guns, Hasidic men in packs of 4 or more) I find waist level finder point and shoot, any old folder avoids suspicion. When I have been confronted I gauge my response based on their level of anger. For angry people I assert my rights and reassure them I'm an artist by explaining the "project" i'm working on and perhaps I'm a student or professor from the famous art college 10 blocks away.