I tell all my dates early on before we meet that I'm an award-winning slut. If they react anything less than wow, I wish them good luck finding their wow with someone else, and fuck off.
Happy open relationships exist. Predominantly polyamorous people would feel trapped in monogamy, and overwhelm their partner with their excess need for intimacy they cannot quench elsewhere. Just like you can manage your friendships, poly people can manage their relationships the same way. They can usually tell if they're polysaturated.
Being lonely is the biggest pressure for me.