There's a huge on-going debate in many discussion fora regarding the topics of STI's, barrier usage, safer-sex practices, and how to approach this within poly relationships. I'll be the first to admit that I'm not an expert in STI's, transmission rates for various microbes, likely vectors, and how effective/ineffective barrier usage is in preventing the "sharing" of more than orgasms. I haven't spent hours and hours researching the topic, nor do I whip out statistics to justify or defend my own position on my choices, or the requests I make to my partners regarding safer sex practices.
For me, the idea of making sexual choices about "acceptable risk" as weighted against potential pleasure doesn't get all the way to my decision-making center. It isn't as simple as saying, "Well, my odds of getting an STI from sharing a few orgasms with this person are lower than my odds of getting mowed down by a drunk driver while getting my mail. That seems reasonable, so let's run with it!"
There is certainly a component that is about acceptable physical risk, but, being poly, that doesn't hit me where I live. If I, or my partner, is going to have sex with someone who has an STI, having an emotional context to frame that in feels important to me. Example: Let's say that I'm interested in being physical with someone that has HSV-2. For me, it makes more sense to keep the physical interactions confined to the realm of pleasurable activities that don't involve significant risk of exchange of bodily fluids unless there is potential for an on-going relationship. At that point, the admittedly low-level of risk for transmission can be assessed. All the related parties get to (are requested to) have a conversation about what that might look like, and see if there is sufficient consensus to move forward.
Yep, I don't make the call just for me and let everyone else deal. There are people that are already part of my life, and I prioritize those relationships (dare I say privilege?) more highly than potential connections or pleasure. That doesn't work for everyone, and there is certainly a very honest and morally conscious segment of the poly community that this wouldn't work for. Many prefer to approach sexual behavior from the perspective of each person being responsible for their own sexual health and risk setting. For me, that's a bit antithetical to having a family approach to poly. I remain very sex and pleasure positive. I just choose to empower my existing partners to have input in my sexual decisions, because my decisions impact them.
Each of my partners gets a head's up and opportunity to weigh in on their preferences in advance of any interaction that would have potential to bring slippery bits into proximity. Let's say I'm going to a party where there is some possibility for raucous libidinous excesses; if they have input on how that needs to look for their sense of safety to be maintained, we hash that out before anything happens. If we haven't talked about it, and an opportunity arises, I keep my pants on and my mouth closed. Do I miss out on some possibilities? Sure, but if someone doesn't want to wait long enough for me to go through proper channels and get consensus from my existing partners before boffing, they really aren't my cup of tea anyways.
It isn't all about me. That's a huge part of being poly they way I choose to do it. My partners get to have more input in my decisions than whether they want to use barriers to protect themselves from the potential risks my choices bring to the table. Yes, that means that I choose to curtail my personal freedom at times. That's not being controlled by others. It's choosing to be self-controlled.