OP, I completely understand what you're on about. One of my best mates from primary school had a scent, and several of my close friends have scents too. Yeah I think you're right in saying that it identifies people. It's weird but one of my friends has the same scent as my primary school mate, freaky as.
But being serious now, when a girl asks you to hold their hoody for a second, that smell.... my god that smell.
Some people just don't have a smell though. They don't stink, but they don't have that unique smell. Oh well..
Most people I can think of have a smell and I can even tell the difference with my family living in the same house having different smells. However I was once told by one of my school mates that everyone else had their own smell but that I didn't have one at all, which seemed slightly strange, I don't know if other people would say the same thing or maybe just her.