There's a major difference between a blood donation and an organ donation. The big difference is that in the situation of an organ donation, there is nowhere near enough supply to meet the demand, whereas with blood, we're much closer to being able to supply the need. You certainly hear about shortages of blood, and those are important, but they're usually intermittent and temporary and in one location.
We have come a long way in the last decade in understanding how significant the risks are from various different possible infections an individual may have. Even in the situation of an intravenous drug abuser who may have hepatitis C, we now understand what the risk is to the recipient. The medical team has the ability to come up with the decision and make a recommendation to that individual. The individual, of course, will make the final decision, but we know in that situation, for example, that we can transplant that patient and treat them with very effective anti-hepatitis C drugs afterwards.
In many of these situations we have much better information about the risk involved, so your family would be presented with that situation, as would the potential recipient, and they can make a decision to go forward.