I guess it depends on what I observe. If they're younger, I'll definitely come over and see if I can help. If they're older I do stop and question whether I'm willing to put myself in to a potentially drama filled situation first. How much do I want to get involved? I'll more than likely make a move to offer them some generic comfort and support either way: smiling at them, hand on the shoulder, checking to make sure they're 'ok'... that sorta thing.

I'd need to feel pretty comfortable with what's going on to offer an ear or any other help though. Maybe I'm just becoming cynical as I get older.