According to the Red Cross, 43,000 pints of blood are used each day. That means 15,695,000 pints of blood are donated per year. Actually a lot more than that, since many donated pints are used only for research or don't get used. But it's a fair estimate to use that number as the number of pints of blood that get donated by the general public in a year.
The same source says that "one pint of blood can save up to three lives," but there's no statistics about how many lives are saved per any quantity of blood donations. Many patients require multiple pints and not all of them live. And it's impossible to say whether a pint of blood saved a life because a life is saved by a number of things: the actions of doctors and nurses and emergency crews of all sorts, the presence of all kinds of equipment and supplies, and many more causes too varied to count and too interrelated to isolate. Still, it's fair to say that out of every hundred pints donated, there must be a few lives saved that would not have been if those pints hadn't been donated. Probably a lot more, but I'm being excessively conservative.
Current federal regulations prevent the donation of blood by any male who has ever had sexual contact with another male since 1977, even if it was one time decades ago and the person has been repeatedly demonstrated to be free of any resulting HIV or other infection. This even includes those whose sexual contact was non-consensual. While the estimate that 10% of the population is gay is widely accepted (though still debated), I can find no reliable estimate of what percentage of the male population is bisexual enough to have experimented at least once. Let's be conservative again and estimate that 15% of the male population is rendered ineligible forever by this rule, regardless of whether they actually have any real risk of having HIV or any other contraindication for blood donation.
Also, a woman who's had sex with a man in the previous category is ineligible for a year. Not a year from the act, but a year from the day she first admitted that act to the Red Cross, which is inexplicable. But let's ignore that. I think we can even ignore this factor entirely.
There's no statistics available which provide any reason to think there's any correlation between the 15% ineligible due to this rule, and a higher or lower likelihood of going to blood drives, and I think it's reasonable to assume that this 15% would be about as likely as the rest of the population to do so, in aggregate. (About 10% of eligible people donate.) Also note that while people can be ineligible for many other reasons (such as foreign travel), there's no particular reason for that to be more or less prevalent in the 15% affected by this rule than the other 85%.
So if 15,695,000 pints were donated by the 85% who could, it follows that about 18,464,705 would have been donated if not for that rule. Thus, 2,769,705 pints are being discarded every year because of that rule. Thus, at least tens of thousand lives are being lost every year because of that rule.
Are other lives being saved because of it? Perhaps. HIV testing on blood samples is vastly, vastly more accurate (and cheaper) than it was in the early 80s when this rule was put into place, but it's probable that somewhere in that almost-three-million pints, there might be a tiny increase in the number of infected pints that slip through. I have no statistics for this, but my gut feeling says that the increase would be negligible. A bigger factor is probably public confidence: the idea that somewhere in the blood supply there's a pint that carries something deadly that you could get in the ER makes people avoid emergency care, even if the odds are so tiny and the dangers of not going to the ER are vastly bigger. And people could even imagine that there's a chance of getting HIV by donating blood, and however unfounded that fear is, if it scares off a few million people, it could cost more pints than it saves. But a quarter-century after the panic of the HIV scare, would that really scare off more donors or patients than it would save?
I don't have any empirical evidence for any of this, but I think it's vastly likely that modernizing those rules about blood donation could save thousands of lives, maybe a lot more. The rules are simply an artifact of a time when HIV was new, and a few highly-publicized cases of it being taken insufficiently seriously by the government and the Red Cross eroded confidence, and in the panic very strict rules were put into place, and after 25 years of improvements in screening technologies and of understanding, the rules have not been substantially revised. And many thousands of people are dying as a result. It's time to look at the numbers, research the factors which I had to estimate, and then make the changes necessary.