I've got to comment on risks, since there seems to be a lot of bizarre logic going on. I'm not going to state exact risks, because the people that don't want to use a condom will find the risk they want, and the people using condoms will find a different one. I want to comment on relative risk.
FYI, many people (studies will vary, but it's sizeable) have an STD and don't know it. Many others (some in this thread) think an STD is such a dumb thing to worry about, it would be stupid of them to tell you about theirs, because you'll miss out on great sex for no good reason. Many other people feel that if they have it, then it's no big deal for you to have it either, besides, they can convince themselves that the odds of you getting it from them are lower than being struck by lightning. Therefore, ASKING PEOPLE IF THEY HAVE IT IS NOT THE SAME AS TESTING! It's not about them being "nice", it's about them being humans and we are really good at denying facts we don't like.
Oral has lower (in some cases none) transmission rates that vaginal or anal sex, if you don't have any open sores in your mouth. Keeping the semen out of your mouth lowers it even further (for diseases present in semen). It still can make sense to use a condom during PIV and PIA, even if you choose not to during oral.
Some argue that test results are useless since you've probably had sex since the test, and the test may have missed one you just got anyway. This sounds like logic, but let me explain why that's so dumb you almost can't have thought about it and still believe it. Here goes my reasoning on why the test is far better than no test. Take an example guy named Rod. Rod has been sexually active for 10 years, with an average of 10 partners per year for 100 total. Suppose I tell you that Rod has HIV. Now, what are the odds that he got it from the last sex parner? That's right, it's 1%. So, if Rod had gotten a test a month ago, there's a 99% chance that the test would have found his HIV, and only a 1% chance that it missed it due to being a month old.
So, if you run across somebody like Rod that passed a test a month ago, then there's a 1% chance that test is fooling you. Let's add in some more fluff for various other reasons (test inaccuracy or ?), and call it a 5% chance that the test is fooling you. There are people that will tell you (I've read it on this board), that a month old test is no better than no test at all, so you might as well just never use condoms. As you can see by my example, the chances of getting an STD from somebody that tested clean a month ago is about 95% lower than the chances of getting one from a similar individual who's never been tested. If I can lower my odds by 95%, I'm pretty happy.
People will tell you that your long term partner could be cheating on you without using condoms, so you might as well swing without condoms since the risk is there. Again, let's look at relative risk here. If my wife is cheating unprotected, it's got to be with a fairly limited group and certainly a limited number of times per month (I'm with her most of the time). The chances that she will contract something from that limited pool are much lower than the odds we will catch something from both of us perusing clubs unprotected. Just as a pure numbers game, the fact that she MIGHT be cheating ONCE IN A WHILE, doesn't compare to throwing the condoms out the window at a gangbang. The numbers are not the same.
The thing about STDs is that a sizable percentage of the US has an incurable STD (according to the news, but not this forum), but you'll almost never find somebody that can bring themselves to tell you they have one. It's not in our nature to give away that kind of disparaging information. It's in our nature to fool ourselves into believing whatever we have to believe to keep doing what we love to do. Let me ask you this, do you know any swingers that love the lifestyle so much, they wouldn't stop doing it no matter what? Well, those people aren't going to tell you about their STD (yes, there are exceptions, so don't bother pointing out you found one).
Having said all that, I'll tell you my preference: bareback. I can enjoy the mechanical parts of sex with a condom on, but I pretty much will never orgasm, and I only do it to show off. I use condoms just long enough to decide if we might be compatible enough for a long term relationship. I realize there's risk, but there's less risk in long term relationships. That's the best I can do.
Everybody else will do whatever they want, and I only wish them to do so with a full understanding of the relative risks.