Others have already made the point. We have been exploring the life -saving possibilities of blood transfusions for a long time now, and we have learnt a lot about the risks of blood transfusions over that period.
Its all about relative risk. Use of blood transfusion has meant that procedures and treatment protocols are available that otherwise could not be used without transfusion support. The awareness of risk is always present, and is used when measuring best practice. Blood use for elective surgery is being driven down and down, with the use of intra-operative cell salvage, laparoscopic surgery and blood substitutes, such as plasma volume expanders and IV fluids becoming every more the norm.
The JW rejection of blood transfusion seems to be entirely on religious grounds, and, to me at least, seems to be based upon a basic misconception, one brought about by the inability of literalist interpreters of the bible to move with the times and the changing and advancing technology. Its yet another reason to be wary of such religions.Through such ridiculous views, they tied themselves into legal knots over the definition of what constituted a blood product or not, some happy to accept products derived from blood, such as factor 8 for the treatment of haemophilia, or anti-D immunoglobulin for the prevention of Haemolytic Disease of the Newborn - Others within the same church would not accept such compromises.
Actually though, due to the law of unintended consequences, JW intrasigence over blood transfusions has actually helped to drive medical practice towards reducing the amounts of blood used in surgical procedures and in the treatment of anaemia, as well as proving a spur towards the development of blood substitutes, and synthetic blood. Thats not to say that such research would not have been done anyway - the risks of an incompatible transfusion reaction or the transmission of a blood borne virus are very well understood - but it probably helped to accelerate such research.