I find that to be fluid bonded with anyone that I have to know and trust everyone who is involved right to the edges of the poly configuration. Any time that changes (someone takes on a partner who has many other partners) I'm more than happy to go back to barrier use. I'm not only responsible for my own health but I am also responsible for my partners' health (and thier partners as well). The only person I can control is myself and as such I'm willing to take the responsibility of using barriers.
Everything will be ok in the end. If it's not ok it's not the end.