I've been non-monogamous ever since I started dating (at first I used the phrase "open relationship", but it might be a bit closer to poly). Right now I like to have one nesting partner, but completely exclusive relationships never made sense to me. For me, being affectionate (even very affectionate!) with whoever I have chemistry with is just lovely, and doesn't tarnish any individual relationship as long as everyone is open about what they want and how they feel. I've noticed that it seems to be becoming more common, but I wish it were more socially acceptable!