A small study of HIV- New York gay men who use party drugs and have had unprotected sex recently looked into whether they'd be less likely to use condoms if PrEP (taking anti-retrovirals while negative to keep from getting HIV) could be shown to reduce the risk of HIV. Here's what they found:
The investigators found that the availability of 80% effective PrEP could reduce inhibitions about unprotected sex. Their results also showed that it could lead men to view unprotected sex as having an acceptable level of risk. [...]
Two psychological mechanisms could lead to PrEP increasing sexual risk taking. The first is "behavioural disinhibition". This means that individuals who desire unprotected sex would view PREP as a substitute for behavioural control, or condom use.
It is also possible that PrEP could lead to "risk compensation". Some individuals may consider that PrEP reduces the risk of HIV transmission to such an extent that they are willing to have unprotected sex when taking PrEP. [...]
A clear majority of men (69%) said that they would be likely to use PrEP if it was shown to be at least 80% effective.
Of course, this group isn't representative of all gay men. But people who have messed up recently and had sex with someone without a condom are the people this drug should be aimed at; while 80% isn't as effective as regular, proper condom usage, some people aren't using condoms regularly already. The question is whether they'll drop off condom usage in large enough numbers to cancel out any positive effect of PrEP.
PrEP seems like it'll be the next big thing. According to the CDC, thousands of people are involved in dozens of studies right now on the effectiveness on PrEP and various PrEP drugs, and promising results in non-human animals have been shown. Results for human populations should start being released soon, and the question will move from whether or not they work to whether or not they should be marketed, and how.
While they stress monogamy and abstinence as the first-line of defense against HIV, they don't work for everyone. And while condoms are still better than the results expected from PrEP, they don't work for everyone as well. People mess up. Few people like condoms more than condom-less sex (and I've never met any of them). They get drunk or take drugs before having sex. They assume that the person they're having sex with is HIV- even if they don't have a reason to. They make bad decisions, and lots of men are looking for excuses to not use condoms.
But it seems to me that if they're already messing up on the condom usage, taking a drug daily that has large side-effects might be hard as well. That is, of course, what these studies are probably looking into. It's easy to force a lab rat to take a drug, but a real human with a real life? Let's see if they actually do it.
People are in charge of their own bodies and are free to make their own informed decisions, but when it comes to public health the question is how best to advertise various safer sex measures. PrEP is available right now (at least in France, and the linked article mentions that several study participants had already tried it in New York), but for it to become a public health measure it still has to prove its effectiveness.