I have just read every post on this thread. I admire others who are giving and willing to go through some pain to benefit another human.
While I am sure some believe that blood saves lives I know first hand that blood transfusions are dangerous. Dangerous for the same reasons some of you are complaining; screening out all those who have transmitable diseases. Often the screening process is highly inadequate. Subsequenty I had a friend die directly caused by a blood transfusion given needlessly by a doctor. Blood is money to medical instutions and doctors as it adds to the bill of patients.
Think I am wrong. Then why are there more and more bloodless hospitals than ever before?
http://www.sabm.org/hospitals/
Sorry if this offends your chosen action to help humanity but this threads needs a little balancing out.